Clinical use of Gonadotropin-Releasing Hormone (GnRH) Agonists in Companion Animals: An Overview

In dogs, cats, ferrets, and pet birds, reproductive physiology is under the control of the hypothalamic­pituitary­-gonadal (HPG) axis. Many hormones are responsible for estrus and reproduction, the most significant being luteinizing hormone (LH), follicle stimulating hormone (FSH), and gonadotropin-releasing hormone (GnRH). Short-lived GnRH is released in a pulsatile fashion from the hypothalamus and acts on the pars distalis of the pituitary gland to stimulate the synthesis and release of the gonadotropins, FSH and LH (Figure 1). Secretion of these gonadotropins into the circulation lead to changes gonadal hormone production and reproductive function.

Figure 1: Regulation of gonadal secretion via the hypothalamic-pituitary-gonadal axis.

Chemical modification of the native short-acting GnRH molecule has led to development of long-acting, potent GnRH agonists, which have been used as a medical means of management for a number of reproductive issues and diseases of companion animals (1-3). GnRH agonists may either stimulate estrus or effectively sterilize the patient, depending on the duration of action and the dosage applied. These agents work by initially stimulating gonadotrophin secretion, followed shortly thereafter with desensitization of the GnRH receptor to the GnRH agonist (Figure 2). This results in a temporary but long-term, fully-reversible down-regulation of gonadotrophin secretion, leading to suppression of reproduction function in both male and female animals (4).

Figure 2: GnRH agonists initially stimulate pituitary LH and FSH secretion, followed by desensitization and down-relation of gonadotrophin secretion.

In recent years, effective low-dose, slow-release implants containing potent GnRH agonists have been released for use in veterinary medicine, especially in Europe and Australia. In companion animals, the deslorelin implant (Suprelorin, Virbac) is the most commonly GnRH agonist used in small animals (5). Deslorelin implants work by lowering pituitary gonadotrophin section. This is not a permanent change but depending on the deslorelin dose, can last up to many months. The implant does not have to be removed, but subsequent doses are needed to sustain the effect.

Unfortunately, GnRH agonist availability is limited in the United States. Although there are GnRH agonists available that are approved for the treatment of human diseases, such as prostate cancer, they are costly and not financially feasible for a pet owner to consider. To date, deslorelin acetate (Suprelorin, Virbac Animal Health, Fort Worth, TX, USA) is the only GnRH agonist that is currently available in the United States but only for the treatment of adrenal disease in ferrets (6). However, it is not legal to use Suporelin in non-ferret species in the United States and extra-label use is explicitly prohibited.

The aim of this blog is to review the applications and treatments of the deslorelin (GnRH agonist) currently used in companion animal medicine.

Deslorelin Use in Intact Male Dogs
In male dogs treated with deslorelin, this GnRH agonist leads to decreased gonadotropins secretion and resultant lowered plasma testosterone concentrations, decreased testicular volume, and azoospermia (1-3,7-9). However, the response to this GnRH agonist can be very variable from one dog to another, and the duration of inhibition of testosterone secretion depends both on the concentration of the deslorelin implant and the size of the dog.

Many studies have confirmed that use of GnRH agonists for reversible chemical sterilization in male dogs is both safe and well-tolerated (7-9). Furthermore, repeated implantation can be used to maintain circulating testosterone at low concentrations. If the deslorelin implants are stopped, the treated dogs will regain normal serum testosterone levels within a few weeks, with full recovery of seminal quality once the GnRH implant has lost its efficacy (10,11).

In addition to contraception, GnRH agonists have also been used to reduce the size of the prostate gland, an effect that may be useful in dogs with benign prostatic hyperplasia (12-14).

Deslorelin in Intact Male Cats
As in dogs, GnRH agonists are gaining increased importance in feline reproductive medicine (2,3,15). In intact male cats, deslorelin implants induce chemical sterilization, as in dogs. In these cats, testosterone concentrations decline rapidly to undetectable values by 3 weeks after implantation and remain low for weeks in the majority of the tomcats treated. As the circulating testosterone falls, the testicular volume decreases and penile spines disappear.

However, high individual variability has been reported, with the duration of efficacy varying between 6 and 24 months (15-17). Similar to dogs, it is possible to use repeated implantation of deslorelin to sustain the drug’s effect.

Deslorelin in Intact Bitches
Although deslorelin implants are only approved for male dogs in Europe (and again, not at all in the USA), studies have been performed in the bitch to investigate its use either as a contraceptive or a method of estrus induction (1-3,18-20).

The first step in the mechanism of action of all GnRH agonists is the stimulation in FSH and LH secretion (so-called "flare-up effect") (4). This followed within a few days by a profound hypogonadal effect (i.e., decrease in FSH and LH levels), which is achieved through receptor down-regulation by internalization of receptors. Generally this induced and reversible hypogonadism is the therapeutic goal, as noted above for the male dogs and cats (1-3).

The initial stimulating effect on gonadotrophin secretion is more pronounced in females than in males (18,19). Thus, estrus induction will be observed in the majority of bitches implanted in anestrus. If pregnancy is achieved, most recommend removal of the deslorelin implant either at the beginning of proestrus, at the time of the LH surge, or at the time of ovulation (2,3,18,19). However, some have reported that some bitches carried their pregnancies to term without the implant being removed, suggesting that down-regulation of gonadotrophin secretion may not be strong enough to induce luteal failure in all bitches.

For use as a contraceptive method, the main problem with using deslorelin implants in female dogs is estrus induction, as discussed above (20). For this reason, deslorelin implants cannot be considered a viable alternative to other, current used contraception in bitches.

Deslorelin in Intact Queens
In contrast to female dogs, the main indication for the use of deslorelin in the female queen is estrus inhibition. Studies have confirmed that this GnRH agonist can be used to effectively suppress ovarian activity (15,20-22), but the duration of inhibition was highly variable among the individual queens depending on the dosage administered. However, deslorelin generally suppresses ovarian activity for many months.

Deslorelin in Spayed Bitches with Urinary Incontinence
Ovariectomy results in elevated circulating concentrations of pituitary LH because of the lack of gonadal negative-feedback on the pituitary gland. LH receptors are present throughout the canine urinary tract (23-25), and it has been postulated that elevated gonadotropins may contribute to the development of urethral sphincter mechanism incompetence (26,27).

Treatment of bitches with long-acting GnRH agonists, such as delorelin, downregulates LH secretion for prolonged time periods and temporarily restores continence to incontinent bitches for varying durations, ranging from 50-738 days (26,27). Similar to alpha-adrenergic agonists (e.g., phenylpropanolamine; PPA), GnRH agonists are not completely effective for the treatment of this urinary incontinence. However, unlike PPA, no adverse effects to GnRH agonists have been reported.

Deslorelin in Ferrets with Adrenal Disease
As in dogs and cats, deslorelin is also a promising and suitable method for contraception in ferrets (28-31). However, GnRH agonists are useful in medical management of ferrets suffering from adrenal disease (hyperadrenocorticism) a common disease in castrated males and females (32-34). In one study of ferrets with adrenal disease, the clinical signs (e.g., vulvar swelling, pruritus, sexual behavior, and aggression) were reduced or markedly suppressed within 14 days of implantation of the deslorelin (34). The time for signs to recur in these ferrets ranged from 8.5–20.5 months (34).

References:

1. Trigg TE, Doyle AG, Walsh JD, et al. A review of advances in the use of the GnRH agonist deslorelin in control of reproduction. Theriogenology 2006;66:1507-1512. 
2. Fontaine E, Fontbonne A. Clinical use of GnRH agonists in canine and feline species. Reprod Domest Anim 2011;46:344-353. 
3. Lucas X. Clinical use of deslorelin (GnRH agonist) in companion animals: a review. Reprod Domest Anim 2014;49 Suppl 4:64-71. 
4. Ortmann O, Weiss JM, Diedrich K. Gonadotrophin-releasing hormone (GnRH) and GnRH agonists: mechanisms of action. Reprod Biomed Online 2002;5 Suppl 1:1-7. 
5. Suprelorin (deslorelin acetate). Summary report from the European Medicines Agency. 
6. Suprelorin F. Package insert. Fort Worth, Texas: Virbac Animal Health 
7. Junaidi A, Williamson PE, Martin GB, et al. Pituitary and testicular endocrine responses to exogenous gonadotrophin-releasing hormone (GnRH) and luteinising hormone in male dogs treated with GnRH agonist implants. Reprod Fertil Dev 2007;19:891-898. 
8. Junaidi A, Williamson PE, Martin GB, et al. Dose-response studies for pituitary and testicular function in male dogs treated with the GnRH superagonist, deslorelin. Reprod Domest Anim 2009;44:725-734. 
9. Romagnoli S, Siminica A, Sontas BH, et al. Semen quality and onset of sterility following administration of a 4.7-mg deslorelin implant in adult male dogs. Reprod Domest Anim 2012;47 Suppl 6:389-392. 
10. Trigg TE, Wright PJ, Armour AF, et al. Use of a GnRH analogue implant to produce reversible long-term suppression of reproductive function in male and female domestic dogs. J Reprod Fertil Suppl 2001;57:255-261. 
11. Gentil M, Hoffmann B, Spang A, et al. Restart of steroidogenesis in dogs during recrudescence of testicular function following downregulation with a GnRH-agonist implant. Cell Tissue Res 2012;350:513-523. 
12. Vickery BH, McRae GI, Bonasch H. Effect of chronic administration of a highly potent LHRH agonist on prostate size and secretory function in geriatric dogs. Prostate 1982;3:123-130. 
13. Nizanski W, Levy X, Ochota M, et al. Pharmacological treatment for common prostatic conditions in dogs - benign prostatic hyperplasia and prostatitis: an update. Reprod Domest Anim 2014;49 Suppl 2:8-15. 
14. Polisca A, Orlandi R, Troisi A, et al. Clinical efficacy of the GnRH agonist (deslorelin) in dogs affected by benign prostatic hyperplasia and evaluation of prostatic blood flow by Doppler ultrasound. Reprod Domest Anim 2013;48:673-680. 
15. Goericke-Pesch S, Wehrend A, Georgiev P. Suppression of fertility in adult cats. Reprod Domest Anim 2014;49 Suppl 2:33-40. 
16. Goericke-Pesch S, Georgiev P, Antonov A, et al. Clinical efficacy of a GnRH-agonist implant containing 4.7 mg deslorelin, Suprelorin, regarding suppression of reproductive function in tomcats. Theriogenology 2011;75:803-810. 
17. Goericke-Pesch S, Georgiev P, Fasulkov I, et al. Basal testosterone concentrations after the application of a slow-release GnRH agonist implant are associated with a loss of response to buserelin, a short-term GnRH agonist, in the tom cat. Theriogenology 2013;80:65-69. 
18. Volkmann DH, Kutzler MA, Wheeler R, et al. The use of deslorelin implants for the synchronization of estrous in diestrous bitches. Theriogenology 2006;66:1497-1501. 
19. Fontaine E, Mir F, Vannier F, et al. Induction of fertile oestrus in the bitch using Deslorelin, a GnRH agonist. Theriogenology 2011;76:1561-1566. 
20. Maenhoudt C, Santos NR, Fontaine E, et al. Results of GnRH agonist implants in oestrous induction and oestrous suppression in bitches and queens. Reprod Domest Anim 2012;47 Suppl 6:393-397. 
21. Goericke-Pesch S. Reproduction control in cats: new developments in non-surgical methods. J Feline Med Surg 2010;12:539-546. 
22. Goericke-Pesch S, Georgiev P, Atanasov A, et al. Treatment of queens in estrus and after estrus with a GnRH-agonist implant containing 4.7 mg deslorelin; hormonal response, duration of efficacy, and reversibility. Theriogenology 2013;79:640-646. 
23. Coit VA, Dowell FJ, Evans NP. Neutering affects mRNA expression levels for the LH- and GnRH-receptors in the canine urinary bladder. Theriogenology 2009;71:239–47.
24. Ponglowhapan S, Church DB, Khalid M. Differences in the expression of luteinizing hormone and follicle-stimulating hormone receptors in the lower urinary tract between intact and gonadectomised male and female dogs. Domest Anim Endocrinol 2008;34:339-351. 
25. Reichler IM, Welle M, Sattler U, et al. Comparative quantitative assessment of GnRH- and LH-receptor mRNA expression in the urinary tract of sexually intact and spayed female dogs. Theriogenology 2007;67:1134–42.
26. Reichler IM, Hubler M, Jöchle W, et al. The effect of GnRH analogs on urinary incontinence after ablation of the ovaries in dogs. Theriogenology 2003;60:1207–16.
27. Reichler IM, Jöchle W, Piché CA, , et al. Effect of a long-acting GnRH analogue or placebo on plasma LH/FSH, urethral pressure profiles and clinical signs of urinary incontinence due to sphincter mechanism incompetence in bitches. Theriogenology 2006;66:1227–36.
28. Schoemaker NJ, van Deijk R, Muijlaert B, et al. Use of a gonadotropin releasing hormone agonist implant as an alternative for surgical castration in male ferrets (Mustela putorius furo). Theriogenology 2008;70:161-167. 
29. Prohaczik A, Kulcsar M, Trigg T, et al. Comparison of four treatments to suppress ovarian activity in ferrets (Mustela putorius furo). Vet Rec 2010;166:74-78. 
30. Goericke-Pesch S, Wehrend A. The use of a slow release GnRH-agonist implant in female ferrets in season for oestrus suppression. Schweiz Arch Tierheilkd 2012;154:487-491. 
31. van Zeeland YR, Pabon M, Roest J, et al. Use of a GnRH agonist implant as alternative for surgical neutering in pet ferrets. Vet Rec 2014;175:66. 
32. Rosenthal KL, Peterson ME, Quesenberry KE, et al. Hyperadrenocorticism associated with adrenocortical tumor or nodular hyperplasia of the adrenal gland in ferrets: 50 cases (1987-1991). J Am Vet Med Assoc 1993;203:271-275. 
33. Schoemaker NJ, Teerds KJ, Mol JA, et al. The role of luteinizing hormone in the pathogenesis of hyperadrenocorticism in neutered ferrets. Mol Cell Endocrinol 2002;197:117-125. 
34. Wagner RA, Piche CA, Jochle W, et al. Clinical and endocrine responses to treatment with deslorelin acetate implants in ferrets with adrenocortical disease. Am J Vet Res 2005;66:910-914. 

Top Endocrine Publications of 2014: Canine and Feline Reproductive Endocrinology

As I've done for the last 5 years, I’ve now finished compiling a fairly extensive list of references concerning canine and feline endocrinology that were written last year (in 2014). I’ll be sharing these with you over the next few months, as well as reviewing a few of the best papers from my lists of clinical endocrine publications.

In my last post, I provided my last list for the 2013 papers on canine and feline endocrine reproduction, so I've decided to start this year off with papers that deal with the same theme of endocrine disorders of the canine and feline gonads, prostate, and mammary gland.

Listed below are 23 papers published in 2014 that deal with a variety of topics of importance for reproductive endocrinology in dogs and cats. These range from the identification and study of kisspeptin (a protein ligand that activate GnRH neurons) in dogs (1) to the use of relaxin measurements to diagnose pregnancy status (2); as well as from a study of the effects of GnRH agonist and antagonists during the postnatal period in cats (3) to the effects of GnRH immunization for treatment of urinary incontinence in spayed bitches (4).

Other publication included studies dealing with suppression of fertility in dogs and cats (4-6,12,13,14,21) to endocrinologic investigations of pyometra (9), ovarian cysts (10), mammary neoplasia (16,19), and benign prostatic hyperplasia and prostatitis (17); and finally, from a study of oxytocin and social bonding in dogs (20) to a review of the influence of sex hormones on seizures in dogs and man (22).

References:

1. Albers-Wolthers KH, de Gier J, Kooistra HS, et al. Identification of a novel kisspeptin with high gonadotrophin stimulatory activity in the dog. Neuroendocrinology 2014;99:178-189.
2. Bergfelt DR, Peter AT, Beg MA. Relaxin: a hormonal aid to diagnose pregnancy status in wild mammalian species. Theriogenology 2014;82:1187-1198.
3. Carranza A, Faya M, Merlo ML, et al. Effect of GnRH analogs in postnatal domestic cats. Theriogenology 2014;82:138-143.
4. Donovan CE, Gordon JM, Kutzler MA. Gonadotropin-releasing hormone immunization for the treatment of urethral sphincter mechanism incompetence in ovariectomized bitches. Theriogenology 2014;81:196-202.
5. Fagundes AK, Oliveira EC, Tenorio BM, et al. Injection of a chemical castration agent, zinc gluconate, into the testes of cats results in the impairment of spermatogenesis: a potentially irreversible contraceptive approach for this species? Theriogenology 2014;81:230-236.
6. Favre RN, Bonaura MC, Praderio R, et al. Effect of melatonin implants on spermatogenesis in the domestic cat (Felis silvestris catus). Theriogenology 2014;82:851-856.
7. Goericke-Pesch S, Wehrend A, Georgiev P. Suppression of fertility in adult cats. Reprod Domest Anim 2014;49 Suppl 2:33-40.
8. Hoglund OV, Hagman R, Olsson K, et al. Intraoperative changes in blood pressure, heart rate, plasma vasopressin, and urinary noradrenalin during elective ovariohysterectomy in dogs: repeatability at removal of the 1st and 2nd ovary. Veterinary Surgery 2014;43:852-859.
9. Jitpean S, Holst BS, Hoglund OV, et al. Serum insulin-like growth factor-I, iron, C-reactive protein, and serum amyloid A for prediction of outcome in dogs with pyometra. Theriogenology 2014;82:43-48.
10. Knauf Y, Bostedt H, Failing K, et al. Gross pathology and endocrinology of ovarian cysts in bitches. Reprod Domest Anim 2014;49:463-468.
11. Kobayashi M, Hori T, Kawakami E. Efficacy of low-dose human chorionic gonadotropin therapy in dogs with spermatogenic dysfunction: a preliminary study. Reprod Domest Anim 2014;49:E44-47.
12. Lucas X. Clinical use of deslorelin (GnRH agonist) in companion animals: a review. Reprod Domest Anim 2014;49 Suppl 4:64-71.
13. Maenhoudt C, Santos NR, Fontbonne A. Suppression of fertility in adult dogs. Reprod Domest Anim 2014;49 Suppl 2:58-63.
14. Marino G, Rizzo S, Quartuccio M, et al. Deslorelin implants in pre-pubertal female dogs: short- and long-term effects on the genital tract. Reprod Domest Anim 2014;49:297-301.
15. Meloni T, Comin A, Rota A, et al. IGF-I and NEFA concentrations in fetal fluids of term pregnancy dogs. Theriogenology 2014;81:1307-1311.
16. Michel E, Rohrer Bley C, Kowalewski MP, et al. Prolactin--to be reconsidered in canine mammary tumourigenesis? Vet Comp Oncol 2014;12:93-105.
17. Nizanski W, Levy X, Ochota M, et al. Pharmacological treatment for common prostatic conditions in dogs - benign prostatic hyperplasia and prostatitis: an update. Reprod Domest Anim 2014;49 Suppl 2:8-15.
18. Parker K, Snead E. Atypical presentation of ovarian remnant syndrome in a dog. J Am Anim Hosp Assoc 2014;50:e1-5.
19. Queiroga FL, Perez-Alenza MD, Gonzalez Gil A, et al. Clinical and prognostic implications of serum and tissue prolactin levels in canine mammary tumours. Vet Rec 2014;175:403.
20. Romero T, Nagasawa M, Mogi K, et al. Oxytocin promotes social bonding in dogs. Proc Natl Acad Sci U S A 2014;111:9085-9090.
21. Schafer-Somi S, Kaya D, Gultiken N, et al. Suppression of fertility in pre-pubertal dogs and cats. Reprod Domest Anim 2014;49 Suppl 2:21-27.
22. Van Meervenne SA, Volk HA, Matiasek K, et al. The influence of sex hormones on seizures in dogs and humans. Vet J 2014;201:15-20.
23. Volta A, Manfredi S, Vignoli M, et al. Use of contrast-enhanced ultrasonography in chronic pathologic canine testes. Reprod Domest Anim 2014;49:202-209.

Top Endocrine Publications of 2013: Canine and Feline Reproductive Endocrinology

In my tenth compilation of the canine and feline endocrine publications, I’m moving on to endocrine disorders of the canine and feline gonads and mammary gland. Listed below are 20 papers published in 2013 that deal with a variety of topics of importance for reproductive endocrinology in dogs and cats.

Of all of these publications, one of the most common and clinically useful topics involves the use of gonadotropin-releasing hormone (GnRH) agonists for management of a variety of disorders. These include the use of GnRH agonist for treatment of queens in estrus and after estrus (3), for reproductive control in queens (4) and tom cats (5), and in dogs affected by benign prostatic hyperplasia (12).

On my next blog post, I will review the mechanism of action for the GnRH agonists, along with their many potential uses and dosage forms.

References:

1. Adams GP, Ratto MH. Ovulation-inducing factor in seminal plasma: a review. Anim Reprod Sci 2013;136:148-156. 
2. Faya M, Carranza A, Miotti R, et al. Fecal estradiol-17beta and testosterone in prepubertal domestic cats. Theriogenology 2013;80:584-586. 
3. Goericke-Pesch S, Georgiev P, Atanasov A, et al. Treatment of queens in estrus and after estrus with a GnRH-agonist implant containing 4.7 mg deslorelin; hormonal response, duration of efficacy, and reversibility. Theriogenology 2013;79:640-646. 
4. Goericke-Pesch S, Georgiev P, Atanasov A, et al. Treatment with Suprelorin in a pregnant cat. J Feline Med Surg 2013;15:357-360. 
5. Goericke-Pesch S, Georgiev P, Fasulkov I, et al. Basal testosterone concentrations after the application of a slow-release GnRH agonist implant are associated with a loss of response to buserelin, a short-term GnRH agonist, in the tom cat. Theriogenology 2013;80:65-69. 
6. Greenberg M, Lawler D, Zawistowski S, et al. Low-dose megestrol acetate revisited: a viable adjunct to surgical sterilization in free roaming cats? Vet J 2013;196:304-308. 
7. Leroy C, Conchou F, Layssol-Lamour C, et al. Normal canine prostate gland: repeatability, reproducibility, observer-dependent variability of ultrasonographic measurements of the prostate in healthy intact beagles. Anat Histol Embryol 2013;42:355-361. 
8. Luu VV, Hanatate K, Tanihara F, et al. The effect of relaxin supplementation of in vitro maturation medium on the development of cat oocytes obtained from ovaries stored at 4 degrees C. Reprod Biol 2013;13:122-126. 
9. Marino G, Zanghi A. Activins and inhibins: expression and role in normal and pathological canine reproductive organs: a review. Anat Histol Embryol 2013;42:1-8. 
10. Mattoso CR, Takahira RK, Beier SL, et al. Evaluation of von Willebrand factor during pregnancy, lactation and oestrous cycle in bitches affected and unaffected by von Willebrand disease. Reprod Domest Anim 2013;48:416-422. 
11. Nishida CR, Everett S, Ortiz de Montellano PR. Specificity determinants of CYP1B1 estradiol hydroxylation. Mol Pharmacol 2013;84:451-458. 
12. Polisca A, Orlandi R, Troisi A, et al. Clinical efficacy of the GnRH agonist (deslorelin) in dogs affected by benign prostatic hyperplasia and evaluation of prostatic blood flow by Doppler ultrasound. Reprod Domest Anim 2013;48:673-680. 
13. Poppl AG, Mottin TS, Gonzalez FH. Diabetes mellitus remission after resolution of inflammatory and progesterone-related conditions in bitches. Res Vet Sci 2013;94:471-473. 
14. Rota A, Tursi M, Zabarino S, et al. Monophasic teratoma of the ovarian remnant in a bitch. Reprod Domest Anim 2013;48:e26-e28. 
15. Serafim MK, Silva GM, Duarte AB, et al. High insulin concentrations promote the in vitro growth and viability of canine preantral follicles. Reprod Fertil Dev 2013;25:927-934. 
16. Sozmen M, Kabak YB, Gulbahar MY, et al. Immunohistochemical characterization of peroxisome proliferator-activated receptors in canine normal testis and testicular tumours. J Comp Pathol 2013;149:10-18. 
17. Spankowsky S, Heuwieser W, Arlt SP. Does oral administration of the amino acid tyrosine affect oestradiol-17beta concentration and sexual behaviour in the bitch? Vet Rec 2013;172:212. 
18. Trisolini C, Albrizio M, Roscino MT, et al. Leptin and queen ovary: new insights about ovulation. Res Vet Sci 2013;94:707-710. 
19. Tvarijonaviciute A, Carrillo-Sanchez JD, Ceron JJ. Effect of estradiol and progesterone on metabolic biomarkers in healthy bitches. Reprod Domest Anim 2013;48:520-524. 
20. Wongbandue G, Jewgenow K, Chatdarong K. Effects of thyroxin (T4) and activin A on in vitro growth of preantral follicles in domestic cats. Theriogenology 2013;79:824-832. 

Testing for Retained Testicular Tissue in Neutered Cats with Urine Marking

My patient is a 5-year-old neutered, male DLH that presented for inappropriate urination. He was not neutered until almost a year of age. He primarily urinates on vertical surfaces, the bed, and laundry piles; however, he does generally urinate in his litter box as well. There is one litter box in the house for 2 cats.

On my physical examination, nothing significant was detected. I was able to extrude his penis, and I did not find any penile barbs. I did a baseline testosterone level, which came back as less than 5 nmol/L, normal for a neutered male cat according to the laboratory.

My gut says this cat shows all the signs of behavioral spraying, although the only medical workup for the inappropriate urination has been a routine urinalysis (which was normal). That minimal workup was 11 months ago, and he has continued his occasional spraying ever since, with no progression of signs such as hematuria or or apparent pollakiurua. I did recommend that we do another complete urinalysis with culture, as well as abdominal radiographs to rule out stones etc. That said, I did explain to the owner (the wife) that a behavior problem sounded most likely in this cat. The owner was willing to start him on clomipramine, so I started him on 5.0 mg, PO once daily, warning her it may take 4 weeks to exhibit efficacy, if it is going to work at all.

I'm just wondering what your take would be on usefulness of single testosterone determination? I've read that it is pretty useless, given the natural fluctuations in hormone secretion and that even an intact male cat could normally have a low value. Do you agree?

Do I need a gonadotrophin-releasing hormone (GnRH) stimulation test to ensure that this cat doesn't have retained testicular tissue, which could be contributing to the problem?

My Response:

Basal testosterone determinations generally are not very useful in evaluating dogs and cats with retained testicular tissue. You certainly could do a GnRH stimulation test, which is much more useful than baseline measurements, at least in male dogs (1).  To perform a GnRH stimulation test in a cat, one protocol is to collect a serum sample for testosterone measurement before and 60 minutes after the intramuscular administration of 25 µg of GnRH (Cystorelin; Merial). A 2-fold rise in basal testosterone after GnRH stimulation indicates that functional testosterone tissue (e.g., retained testicle) is present.

Penile barbs in cat

However, we don't generally need to perform basal testosterone measurements or do provocative GnRH stimulation tests on male cats. A intact male cat's penis has a band of about 120–150 backwards-pointing spines, which are about one millimeter long (2).

As you have already reported in this cat, castrated cats will loose their penile barbs. In other words, if there are barbs on the penis, the cat has testosterone in their circulation—if there are no barbs, there is no testosterone. Cats are great that way!

Inappropriate urination is a common problem in male cats, with a prevalence of approximately 10% in neutered males. I'd definitely recommend a workup to exclude lower urinary tract disease (3) but I would also continue to try to convince the owners to add at least one more litter box. In addition, litter box hygiene has been proven to be an important part in treating feline urine marking (4-6). You should also discuss things like identifying triggers and preventing exposure to them (e.g., block access to windows where they may see other cats) and provide more environmental stimulation (7,8).

Flouxetine and clomipramine are of roughly equal efficacy (6,9). With both drugs, it's not uncommon to see noticeable clinical improvement within the first couple of weeks if the drug is going to work. I personally prefer fluoxetine, since it is associated with less side effects.

Bottom Line

Because the finding of spines on a cat's penis indicate the presence of testosterone in the cat's body, these penile spines act as a bioassay for testosterone.

There are other tests we can do (i.e., GnRH or hCG stimulation tests) but in cats, I don't do these —I check the penis. This bioassay is the cheapest and best kind of assay for circulating testosterone in cats.

References:

1. de Gier J, Buijtels JJ, Albers-Wolthers CH, et al. Effects of gonadotropin-releasing hormone administration on the pituitary-gonadal axis in male and female dogs before and after gonadectomy. Theriogenology 2012;77:967-978. 
2. Aronson LR, Cooper ML. Penile spines of the domestic cat: their endocrine-behavior relations. Anat Rec 1967;157:71–78.
3. Tynes VV, Hart BL, Pryor PA, et al. Evaluation of the role of lower urinary tract disease in cats with urine-marking behavior. J Am Vet Med Assoc 2003;223:457-461. 
4. Pryor PA, Hart BL, Bain MJ, et al. Causes of urine marking in cats and effects of environmental management on frequency of marking. J Am Vet Med Assoc 2001;219:1709-1713. 
5. Neilson JC. House soiling by cats In: Horwitz DF, Mills DS, eds. BSAVA Manual of Canine and Feline Behavioural Medicine Second ed. Gloucester: British Small Animal Veterinary Association;, 2009;117–126.
6. Mills DS, Redgate SE, Landsberg GM. A meta-analysis of studies of treatments for feline urine spraying. PLoS One 2011;6:e18448. 
7. Herron ME, Buffington CA. Environmental enrichment for indoor cats: implementing enrichment. Compend Contin Educ Vet 2012;34:E3. 
8. Ellis SL, Rodan I, Carney HC, et al. AAFP and ISFM feline environmental needs guidelines. J Feline Med Surg 2013;15:219-230. 
9. Hart BL, Cliff KD, Tynes VV, et al. Control of urine marking by use of long-term treatment with fluoxetine or clomipramine in cats. J Am Vet Med Assoc 2005;226:378-382. 

Diagnostic Testing for Ovarian Remnant Syndrome in Dogs — Is There a Practical Test?

Layla is a 7-year old obese Golden retriever that had an ovariohysterectomy about 5 years ago. She continued to have heat cycles and her serum progesterone concentrations were high, consistent with a ovarian remnant. About a year after she was first spayed, an exploratory laporatomy was done and an ovarian remnant removed. At time of that exploratory, the surgeon also identified some suspicious tissue that was not removed due to its location right next to the colonic blood supply. The dog did have a couple more heat cycles, then nothing for the last 4 years— until now.

I saw her last week with signs of heat (e.g., vaginal bleeding, slightly swollen vulva). Her vaginoscopy showed no masses, just a lot of blood. She is otherwise clinically normal. Her vaginal cytology examination did not reveal any cornified epithelial cells but showed mostly parabasal and intermediate cells (more intermediates), lots of RBC, and a few WBC. We ran a serum progesterone level and it was low at 3.3 nmol/L.

Could this dog now be having a heat cycle, even though she hasn’t had any signs of estrus for the last 4 years? If so, what is the best way to confirm another ovarian remnant?

• Is vaginal cytology useful?
• I have read about serum luteinizing hormone (LH) levels— is that a good way to check for a remnant?  
• Also how useful would an abdominal ultrasound be in finding the remnant?

I was still wondering how common (or if it is even possible) to go years without any signs of heat in a dog with an ovarian remnant?

My Response:

Diagnosing bitches with ovarian remnant syndrome can be straight-forward or be very challenging, depending on the phase of the reproductive cycle. Vaginal cytology may be useful in diagnosis of an ovarian remnant, but only if the dog presents during proestrus or actual estrus. In many cases, testing may need to be supplemented by one or more determinations of serum estrogen or progesterone concentrations, and even then, the measurement of these sex steroids can yield equivocal results (1-3).

In this dog, the lack of cornified cells on vaginal cytology and low serum progesterone concentrations are not consistent with estrus. Although these findings certainly do not confirm an ovarian remnant, they cannot totally rule out ovarian remnant syndrome either.

Abdominal ultrasonography can be helpful in suspected cases of ovarian remnant syndrome. However, its effectiveness depends on the expertise of the examiner and the size of the ovarian remnant (3,4). In my experience, use of abdominal ultrasound is generally a waste of time and money when trying to rule out an ovarian remnant in the bitch.

A nice screening test to check for the presence of circulating estrogen (which would be expected both in the intact bitch an dogs with an ovarian remnant) is to simply measure a baseline canine luteinizing hormone (LH) concentration (5). In spayed bitches, circulating LH concentrations increase as a result of the loss of negative feedback of ovarian hormones on the pituitary gland after ovariectomy (5-7). In one study, mean plasma LH concentrations were higher in the bitches with ovarian remnant syndrome (4.1 µg/L) than in the unspayed control dogs tested during anestrus (0.64 µg/L) (7). However, the mean LH values were not as high as in the spayed control dogs (20.2 µg/L), suggesting that the ovarian remnant still secretes enough hormone to partially suppress LH secretion. As might be expected, some overlap in plasma LH concentrations between the groups did occur, so the use of the LH test is not a perfect test for diagnosing ovarian remnant syndrome (7).

One big advantage of the plasma LH test is that it can be run at anytime (i.e., behavioral signs of estrus not necessary to run the LH test), as it is monitoring the negative feedback loop from the ovary to the pituitary gland. It is very important, however, to use the canine LH test and not a human LH test in order to obtain reliable results.

Because a single serum LH determination is not 100% reliable, dynamic stimulation testing with gonadotropin-releasing hormone (GnRH) has been advocated as a more definitive means for distinguishing between spayed bitches and those with an ovarian remnant (6,7). However, GnRH stimulation testing is costly and may require multiple visits and blood samplings in some dogs.

Another option is to submit a basal serum sample to Cornell University for an Anti-Mullerian hormone (AMH) test (8). The ovaries normally secrete AMH and appear to be the sole source of serum AMH in the intact bitch. Following ovariohysterectomy, the serum concentrations of AMH fall to very low levels. Therefore, measuring a serum AMH concentration can be a useful marker to access the presence of ovaries or an ovarian remnant in dogs (8). 

Bottom Line
Although ovarian remnant syndrome is possible in this dog, further hormone testing would certainly is required to make or exclude that diagnosis. However, I would consider it uncommon for a dog with an ovarian remnant to have gone 4 years without any signs of estrus.

So before you embark on a time-consuming and expensive regime of diagnostic tests, I'd recommend that you first question the owner carefully to be certain that there is no other potential sources of exogenous estrogen exposure that could be causing this dog's clinical signs.  Topical hormone replacement creams and sprays are widely used by many pet owners today. If the owner is using these creams and the dog occasionally licks the estrogen from the owner's skin, that could be responsible for the signs of estrus (9,10). Getting a complete history is sometimes the cheapest diagnostic test we have to rule out an ovarian remnant.

References:

1. Feldman EC, Nelson RW. Ovarian cycle and vaginal cytology. In: Canine and Feline Endocrinology and Reproduction, ed. Feldman EC, Nelson RW, 3rd ed, Saunders, St. Louis. 2004;752.
2. Feldman EC, Nelson RW. Infertility, associated breeding disorders, and disorders of sexual development. In: Canine and Feline Endocrinology and Reproduction, ed. Feldman EC, Nelson RW, 3rd ed, Saunders, St. Louis. 2004; 892–893. 
3. Ball RL, Birchard SJ, May LR, et al. Ovarian remnant syndrome in dogs and cats: 21 cases (2000-2007). J Am Vet Med Assoc 2010;236:548-553. 
4. Davidson AP, Baker TW. Reproductive ultrasound of the bitch and queen. Top Companion Anim Med 2009;24:55-63.
5. Lofstedt RM, Vanleeuwen JA. Evaluation of a commercially available luteinizing hormone test for its ability to distinguish between ovariectomized and sexually intact bitches. J Am Vet Med Assoc 2002;220:1331-1335. 
6. Beijerink NJ, Buijtels JJ, Okkens AC, et al. Basal and GnRH-induced secretion of FSH and LH in anestrous versus ovariectomized bitches. Theriogenology 2007;67:1039-1045. 
7. Buijtels JJ, de Gier J, Kooistra HS, et al. The pituitary-ovarian axis in dogs with remnant ovarian tissue. Theriogenology 2011;75:742-751. 
8. Place NJ, Hansen BS, Cheraskin JL, et al. Measurement of serum anti-Mullerian hormone concentration in female dogs and cats before and after ovariohysterectomy. J Vet Diagn Invest 2011;23:524-527. 
9. Parker-Pope T. When hormone creams expose others to risks. New York Times, October 25, 2010. 
10. Lau E. Hormone replacement skin products affect users' pets, confound veterinarians. The VIN News Service 2010. 

Top Endocrine Publications of 2012: Canine and Feline Reproductive Endocrinology

Fertility axis. GnRH, LH and FSH 
stimulate secretion of testosterone, 
progesterone, estrogen, and inhibin. 
Controlled via negative feedback effect
on hypothalamus and pituitary gland.

In my 9th compilation of the canine and feline endocrine publications of 2012, I’m moving on to endocrine disorders of the canine and feline gonads and mammary gland.

Listed below are 23 research papers written in 2012 that deal with a variety of issues of clinical importance in reproductive endocrinology in dogs and cats.

These range from the changes in the pituitary-gonadal axis in dogs with disorders of sexual development (1) to the effects of gonadotropin-releasing hormone (GnRH) in dogs and cats (3,7,18,19); from studies on the ovarian remnant syndrome (4,10,14,18, 22) to a review of the common lesions of the male reproductive tract (5); and from studies of the adrenal sex steroids (6,13) associated with atypical hyperadrenocortisim to studies of the progesterone and prolactin receptors in the mammary gland of cats and dogs (9,12).

Other studies include a review of the reproductive causes of hypocalcemia in dogs and cats (2) to the  reproductive effects of hypothyroidism (15); and finally, from the effects of age and cryptorchidism on plasma levels of insulin-like peptide and testosterone in male dogs (16) to studies investigating the interaction of circulating reproductive hormones on the canine prostate gland (17,23).

References:

1. Buijtels JJ, de Gier J, Kooistra HS, et al. Disorders of sexual development and associated changes in the pituitary-gonadal axis in dogs. Theriogenology 2012;78:1618-1626. 
2. Davidson AP. Reproductive causes of hypocalcemia. Top Companion Anim Med 2012;27:165-166. 
3. de Gier J, Buijtels JJ, Albers-Wolthers CH, et al. Effects of gonadotropin-releasing hormone administration on the pituitary-gonadal axis in male and female dogs before and after gonadectomy. Theriogenology 2012;77:967-978. 
4. Demirel MA, Acar DB. Ovarian remnant syndrome and uterine stump pyometra in three queens. J Feline Med Surg 2012;14:913-918. 
5. Foster RA. Common lesions in the male reproductive tract of cats and dogs. Vet Clin North Am Small Anim Pract 2012;42:527-545, vii. 
6. Ginel PJ, Sileo MT, Blanco B, et al. Evaluation of serum concentrations of cortisol and sex hormones of adrenal gland origin after stimulation with two synthetic ACTH preparations in clinically normal dogs. Am J Vet Res 2012;73:237-241. 
7. Gobello C. Effects of GnRH antagonists vs agonists in domestic carnivores, a review. Reprod Domest Anim 2012;47 Suppl 6:373-376. 
8. Gomes Poppl A, Costa Valle S, Hilario Diaz Gonzalez F, et al. Estrus cycle effect on muscle tyrosine kinase activity in bitches. Vet Res Commun 2012;36:81-84. 
9. Gracanin A, de Gier J, Zegers K, et al. Progesterone receptor isoforms in the mammary gland of cats and dogs. Reprod Domest Anim 2012;47 Suppl 6:313-317. 
10. Gunzel-Apel AR, Buschhaus J, Urhausen C, et al. Clinical signs, diagnostic approach and therapy for the so-called ovarian remnant syndrome in the bitch. Tierarztl Prax Ausg K Kleintiere Heimtiere 2012;40:35-42. 
11. Kim H, Choi H, Choi J. A giant parovarian cyst in a dog with a granulosa cell tumor. J Vet Med Sci 2012;74:385-389. 
12. Michel E, Feldmann SK, Kowalewski MP, et al. Expression of prolactin receptors in normal canine mammary tissue, canine mammary adenomas and mammary adenocarcinomas. BMC Vet Res 2012;8:72. 
13. Monroe WE, Panciera DL, Zimmerman KL. Concentrations of noncortisol adrenal steroids in response to ACTH in dogs with adrenal-dependent hyperadrenocorticism, pituitary-dependent hyperadrenocorticism, and nonadrenal illness. J Vet Intern Med 2012;26:945-952. 
14. Oliveira KS, Silva MAM, Brun MV, et al. Ovarian remnant syndrome in small animals. Semina: Ciências Agrárias, Londrina 2012;33:363-380.
15. Panciera DL, Purswell BJ, Kolster KA, et al. Reproductive effects of prolonged experimentally induced hypothyroidism in bitches. J Vet Intern Med 2012;26:326-333. 
16. Pathirana IN, Yamasaki H, Kawate N, et al. Plasma insulin-like peptide 3 and testosterone concentrations in male dogs: changes with age and effects of cryptorchidism. Theriogenology 2012;77:550-557. 
17. Ponglowhapan S, Church DB, Khalid M. Expression of luteinizing hormone and follicle-stimulating hormone receptor in the dog prostate. Theriogenology 2012;78:777-783. 
18. Rohlertz M, Strom Holst B, Axner E. Comparison of the GnRH-stimulation test and a semiquantitative quick test for LH to diagnose presence of ovaries in the female domestic cat. Theriogenology 2012;78:1901-1906. 
19. Struthers RS. Gonadotropin-releasing hormone targeting for gonadotroph ablation: an approach to non-surgical sterilization. Reprod Domest Anim 2012;47 Suppl 4:233-238. 
20. Switonski M, Payan-Carreira R, Bartz M, et al. Hypospadias in a male (78,XY; SRY-positive) dog and sex reversal female (78,XX; SRY-negative) dogs: clinical, histological and genetic studies. Sex Dev 2012;6:128-134. 
21. Tejerizo G, Domenech A, Illera JC, et al. Altered plasma concentrations of sex hormones in cats infected by feline immunodeficiency virus or feline leukemia virus. Domest Anim Endocrinol 2012;42:113-120. 
22. Urhausen C, Buschhaus J, Wolf K, et al. Identification of ovarian remnant tissue in the bitch after incomplete ovariectomy or ovariohysterectomy. Proceedings of the 7th International Symposium on Canine and Feline Reproduction, 2012. 
23. Wolf K, Kayacelebi H, Urhausen C, et al. Testicular steroids, prolactin, relaxin and prostate gland markers in peripheral blood and seminal plasma of normal dogs and dogs with prostatic hyperplasia. Reprod Domest Anim 2012;47 Suppl 6:243-246. 

What's the Best Way to Confirm Ovarian Remnant Syndrome in Cats?

In the queen, the most common cause of behavioral and physical signs of estrus after ovariohysterectomy is remnant ovarian tissue that has regained folliculogenesis and production of estrogens (1). 

In most cats, the "ovarian remnant syndrome" certainly is caused by failure to completely remove both ovaries at ovariohysterectomy. It is possible to have a small piece of ovarian tissue inadvertently drop back into the abdominal cavity during the spaying procedure and subsequently revascularize, resulting in signs of estrus (2). However, this syndrome can be also associated with the presence of accessory ovarian tissue that can be extremely difficult to detect at the time of routine ovariohysterectomy.

Whether entrapped in a ligature or accidentally dropped into the peritoneal cavity, revascularization of remnants by the omental blood supply can occur (2). The ovarian tissue can remain hormonally functional and even ovulate.  Although this condition is generally called the ovarian remnant syndrome, there is much contention among veterinary surgeons that it is not a syndrome but a surgical error

Diagnosis of ovarian remnant syndrome can sometimes be challenging but is based on a combination of history and clinical signs, vaginal cytology, and hormonal testing (1,3-6).

Vaginal cytology

The first step in the workup of a cat in which ovarian remnant or ectopic ovarian tissue is suspected is to perform vaginal cytology during the time your cat is showing signs of estrus. The only thing that causes a cat's vaginal smear to contain a high number of cornified vaginal epithelial cells is the presence of estrogen. This finding on vaginal cytology is a great bioassay for the presence of high levels of estrogen in the circulation (6).

In general, the use of vaginal cytology as a bioassay for feline estrogen is more accurate than a single serum sample. Vaginal cytological changes in queens in estrus tends to be more subtle than those of dogs but usually include an increase in cornified vaginal epithelial cells and clearing of normal background mucous (6).

Serum estradiol concentrations

Why not simple measure serum estradiol, the main estrogen in the cat? In queens during estrus, estradiol levels rise sharply to more than 20 pg/ml before returning rapidly to basal concentrations in as few as 48 hours. Thus blood sampling for estradiol is generally not helpful because the timing of the sample may not coincide directly with the period of peak estrus activity.

Therefore, the finding of high serum estradiol concentrations (>20 pg/ml) in a cat showing sign of estrus is consistent with ovarian remnant syndrome, the diagnosis can never be excluded if lower levels of estradiol are measured (1).

Serum luteinizing hormone (LH) concentrations

The hormonal serum test that is most useful in this situation is a basal luteinizing hormone (LH) determination (7). For this LH testing, we generally use a commercially available LH assay from Synbiotics. Although originally designed as a canine ovulation timing aid, this LH test may be used to distinguish between ovariohysterectomized and sexually-intact queens (or bitches). One advantage of using the serum LH test over vaginal cytology is it can be run at any time, not just when the cat is showing signs of estrus. If you do LH test, the manufacturer recommends two tests at least 24 hours apart to rule out the LH surge.

In the intact queen, LH is maintained at basal concentrations through the negative feedback influence of ovarian estradiol secretion on the pituitary gonadotropins. Following ovariectomy, this control is lost and LH concentrations increase resulting in a positive test.

Therefore, if a high serum LH concentration is found, then it is unlikely that the cat has any ovarian tissue. On the other hand, if the serum LH is low (less than 1 ng/ml), that indicates there is estrogen present in the circulation suppressing pituitary LH secretion (7). The source of this circulating estrogen could be from either endogenous or exogenous sources. If it's of endogenous origin, that means that the cat does indeed have an ovarian remnant or ectopic ovarian tissue.

The only problem with the use of serum LH determination is that some cats ultimately found to have an ovarian remnant will have falsely high LH values. The reason for this discrepancy in the expected pituitary-ovarian feedback loop is unknown, but it is clear that the finding of a high LH value alone can never rule out an ovarian remnant with 100% certainty. So it's still best to use vaginal cytology in conjunction with the serum LH measurements.

Provocative testing with hCG or GnRH analogues

The most efficient diagnostic aid for ovarian remnant syndrome is a hormone challenge testing (1,3-5). The goal of these stimulation tests is to cause ovulation of a follicle by exogenous LH-like compounds, thus confirming the presence of functional ovarian tissue. 

For these protocols, it is important that the queen be in true estrus. The procedure for testing is as follows:

1. Collect blood needed to measure the basal concentration of serum progesterone (and estradiol if desired).
2. Inject the cat with human chorionic gonadotropin (hCG), 44 IU/kg BW or 250-500 IU total dose, IM.
3. Alternatively, inject the cat with gonadotropin-releasing hormone (GnRH), 2 μg/kg BW or 25 μg total dose, IM.
4. Collect a post-stimulation blood sample for serum progesterone 1-3 weeks later.

Documenting a high serum progesterone level (>2 ng/ml) after hGC or GnRH stimulations confirms a diagnosis of ovarian remnant syndrome (1).

GnRH stimulation testing for cats not currently in estrus

Finally, a recent study demonstrated that measurement of plasma estradiol 2 hours after stimulation with a gonadotropin-releasing hormone (GnRH)-analogue appeared to be a reliable method to diagnose the presence of ovarian tissue in the female cat not currently showing signs of estrus (8).  With this protocol, a serum estradiol concentration greater than 3 pg/ml is consistent with the presence of ovarian tissue.

References:

1. Little SE. Female reproduction. In: Little SE (ed). The Cat: Clinical Medicine and Management. Saunders Elseiver 2012; 1195-1227.
2. DeNardo GA, Becker K, Brown NO, et al. Ovarian remnant syndrome: revascularization of free-floating ovarian tissue in the feline abdominal cavity. Journal of the American Animal Hospital Association 2001;37:290-296.
3. Wallace MS. The ovarian remnant syndrome in the bitch and queen The Veterinary Clinics of North: America Small Animal Practice 1991;21:501-507. 
4. Miller DM. Ovarian remnant syndrome in dogs and cats: 46 cases (1988-1992). Journal of Veterinary Diagnostic Investigation 1995;7:572-574.
5. Ball RL, Birchard SJ, May LR, et al. Ovarian remnant syndrome in dogs and cats: 21 cases (2000-2007). Journal of the American Veterinary Medical Association 2010;236:548-553
6. Mills JN, Valli VE, Lumsden HH. Cyclical changes of vaginal cytology in the cat. Canadian Veterinary Journal 1979;20:95–101.  
7. Scebra LR, Griffin B. Evaluation of a commercially available luteinizing hormone test to distinguish between ovariectomized and sexually intact queens. Proc Am Coll Vet Intern Med Forum 2003. 
8. Axner E, Gustavsson T, Strom Holst B. Estradiol measurement after GnRH-stimulation as a method to diagnose the presence of ovaries in the female domestic cat. Theriogenology 2008;70:186-191.

Top Endocrine Publications of 2011: Canine and Feline Reproductive Endocrinology

In my 9th compilation of the canine and feline endocrine publications of 2011, I’m moving on to endocrine disorders of the canine and feline gonads and mammary gland.

Listed below are 11 research papers written in 2011 that deal with a variety of issues of clinical importance in reproductive endocrinology in dogs and cats.

These range from the investigation of male pseudohermaphroditism in dogs (1) to a report of persistent Müllerian duct syndrome (2); from tumors of the testes (8,11) to ovarian cysts (9) in dogs; from the effects of neutering on circulating concentrations of acute-phase proteins, adiponectin and IGF-1 in dogs (10) to studies investigating the interaction between IGF-1 and apoptosis-associated proteins on canine mammary gland tumors (7).

Finally, we have two papers on feline reproduction: the first (4) is a review of reproductive problems in both the queen (e.g., ovarian remnant syndrome, mammary fibroadenomatous hyperplasia, pregnancy diagnosis) and the tom (e.g., cryptorchidism, low libido). The other paper describes the use of deslorelin acetate, an injectable gonadotropin releasing hormone (GnRH) agonist, as a new way of achieving temporary suppression of estrus (5).

References:

1. Bigliardi E, Parma P, Peressotti P, et al. Clinical, genetic, and pathological features of male pseudohermaphroditism in dog. Reprod Biol Endocrinol 2011;9:12. 
2. Breshears MA, Peters JL. Ambiguous genitalia in a fertile, unilaterally cryptorchid male miniature schnauzer dog. Vet Pathol 2011;48:1038-1040. 
3. Dolka I, Motyl T, Malicka R, et al. Relationship between receptors for insulin-like growth factor- I, steroid hormones and apoptosis-associated proteins in canine mammary tumors. Pol J Vet Sci 2011;14:245-251. 
4. Little S. Feline reproduction: problems and clinical challenges. J Feline Med Surg 2011;13:508-515. 
5. Malik R, Howe P, Hollinshead F. Deslorelin implants - a new choice in feline reproductive medicine. J Feline Med Surg 2011;13:874-875. 
6. Meler EN, Scott-Moncrieff JC, Peter AT, et al. Cyclic estrous-like behavior in a spayed cat associated with excessive sex-hormone production by an adrenocortical carcinoma. J Feline Med Surg 2011;13:473-478. 
7. Pathirana IN, Ashida Y, Kawate N, et al. Comparison of testosterone and insulin-like peptide 3 secretions in response to human chorionic gonadotropin in cultured interstitial cells from scrotal and retained testes in dogs. Anim Reprod Sci 2011;124:138-144. 
8. Saegusa Y, Hayashi H, Taniai E, et al. Spermatocytic seminoma with neuroectodermal differentiation and sertoli cell tumor in a dog. Vet Pathol 2011;48:1024-1028. 
9. Sontas BH, Milani C, Romagnoli S, et al. A huge ovarian cyst in a hysterectomized bitch. Reprod Domest Anim 2011;46:1107-1111. 
10. Tvarijonaviciute A, Martinez-Subiela S, Carrillo-Sanchez JD, et al. Effects of orchidectomy in selective biochemical analytes in Beagle dogs. Reprod Domest Anim 2011;46:957-963. 
11. Vascellari M, Carminato A, Camali G, et al. Malignant mesothelioma of the tunica vaginalis testis in a dog: histological and immunohistochemical characterization. J Vet Diagn Invest 2011;23:135-139. 

Q & A: High Serum Estradiol in a Neutered Male Dog with Alopeica

My patient is a 2-year old male castrated Alaskan Malamute that presented with the main clinical sign of patches of nonpruritic alopecia on the dorsal lumbar area. There is no other hair loss or clinical signs. 

The serum chemistry panel, total and free T4, and TSH concentrations are all normal.

I did an ACTH stimulation test and send serum to the Clinical Endocrinology laboratory at the University of Tennessee for the adrenal sex hormone panel. These are the results, before and after ACTH stimulation:

• Cortisol — Basal value 19 ng/ml (reference range, 2-56 ng/ml) Post-ACTH 96 ng/ml (reference range, 70-151 ng/ml)
• Androstenedione — 0.15 ng/ml (reference range, 0.05-0.3 ng/ml) Post-ACTH 0.76 ng/ml (reference range, 0.24-2.0 ng/ml)
• Progesterone — Basal 0.06 ng/ml (reference range, 03-.17 ng/ml) Post-ACTH 64 ng/ml (reference range, 22-1.45 ng/ml)
• Aldosterone — Basal value 19 ng/ml (reference range, 2-56 ng/ml) Post-ACTH 96 ng/ml (reference range, 70-151 ng/ml)
• Estradiol — Basal value 85 pg/ml (reference range, 23-65 pg/ml) Post-ACTH 75 pg/ml (reference range, 23-69 pg/ml)

My question: what would be the source of the high serum estradiol concentrations? Does it mean anything?

Should I start the dog on melatonin or mitotane?

My Response:

Estradiol (17β-estradiol) is a sex hormone produced in the ovary in the female. In the intact male, estradiol is also present, being produced as an active metabolic product of testosterone (1). In neutered dogs, The adrenal glands do not secrete estradiol directly but do normally secrete adrenal androgens (i.e., androstenedione and testosterone), even in the neutered dogs. A fraction of these adrenal androgens undergoes conversion to estradiol by an enzyme called aromatase in peripheral tissues (especially fat cells).

Conversion of circulating testosterone (steroid on left) to estadiol (on right).
The enzyme aromatase transforms the left-hand ring (the A-ring) of steroids to an aromatic state (hence the name) through oxidation and subsequent elimination of a methyl group.

So the source of the circulating estradiol that you are measuring could indirectly be the adrenal glands, but whether or not the high value found in this dog is clinically significant is difficult to know. These adrenal panels are difficult to interpret, and they are often abnormal in dogs even without clear evidence of typical or atypical Cushing's syndrome (2).

In a recent study of normal dogs published out of the University of Tennessee, they showed that the there was a wide range of variability in estradiol concentration both within and between the dogs (3). In addition, they reported that these estradiol concentrations often exceed the normal ranges established by the laboratory! This may account for why most of the adrenal panels I see have an abnormal sserum estradiol concentration.

Based on that study (3), I would ignore the results of these adrenal panels when the only abnormality is a high serum estradiol concentration.

Alopecia X is a term that has been used to describe dog that show dermatological signs that look similar to that seen with Cushing's disease (e.g., bilaterally symmetric alopecia and hyperpigmentation). This syndrome is common seen in the Nordic breeds, Pomeranians, and Chow chows. The cause of alopecia X is not understood (thus the term alopecia X!), but it is associated with hair cycle arrest.  Adrenal sex hormone abnormalities are no longer believed to play a role (4-6).

Since other labs are normal and since the dog is an Arctic breed, Alopecia X is certainly possible, and a relatively benign treatment such as melatonin can be tried. Click here to see a nice website with more info for vets and owners about alopecia X in Malamutes.

References:

1. Rijnberk A. Kooistra HS. Testes, In: Clinical Endocrinology of Dogs and Cats: An Illustrated Text. Second Edition. Schluetersche 2009.
2. Behrend EN, Kennis R. Atypical Cushing's syndrome in dogs: arguments for and against. The Veterinary Clinics of North America: Small Animal Practice 2010;40:285-296.
3. Frank LA, Mullins R, Rohrbach BW. Variability of estradiol concentration in normal dogs. Veterinary Dermatology 2010;21:490-3.
4. Frank LA, Hnilica KA, Oliver JW. Adrenal steroid hormone concentrations in dogs with hair cycle arrest (Alopecia X) before and during treatment with melatonin and mitotane. Veterinary Dermatology 2004;15:278-284.
5. Frank LA, Donnell RL, Kania SA. Oestrogen receptor evaluation in Pomeranian dogs with hair cycle arrest (alopecia X) on melatonin supplementation. Veterinary Dermatology 2006;17:252-258.
6. Frank LA. Oestrogen receptor antagonist and hair regrowth in dogs with hair cycle arrest (alopecia X). Veterinary Dermatology 2007;18:63-66.