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. 

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 2010: The Canine and Feline Reproductive Endocrinology

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

In my 9th compilation of the canine and feline endocrine publications of 2010, I’m moving on to endocrine disorders of the canine gonads and mammary gland.

Listed below are 9 research papers written in 2010 that deal with a variety of issues of clinical importance in reproductive endocrinology in dogs.

These range from the investigations of the pituitary-ovarian axis in dogs with a functional granulosa cell tumor (1) to studies of the expression of estrogen and progesterone receptors in sebaceous gland tumors (2); and from studies of gonadotropin-releasing hormone (GnRH)-agonist implants in the treatment of reproductive disorders in the male dog (3) to a review of non-surgical methods for reproductive control in cats (4).

Finally, a number of studies investigate markers of malignancy for mammary gland tumors (6,7,8). Finally, the last paper reviews alternative ways to treat benign prostatic hyperplasia, including hormonal suppression of testicular function with GnRH-depot-analogues, inhibition of the 5-alpha-reductase, or peripheral androgen action with anti-androgens (9).

References:

1. Buijtels JJ, de Gier J, Kooistra HS, et al. Alterations of the pituitary-ovarian axis in dogs with a functional granulosa cell tumor. Theriogenology 2010;73:11-19.
2. Ginel PJ, Lucena R, Millan Y, et al. Expression of oestrogen and progesterone receptors in canine sebaceous gland tumours. Veterinary Dermatology 2010;21:297-302.
3. Goericke-Pesch S, Wilhelm E, Ludwig C, et al. Evaluation of the clinical efficacy of Gonazon implants in the treatment of reproductive pathologies, behavioral problems, and suppression of reproductive function in the male dog. Theriogenology 2010;73:920-926.
4. Goericke-Pesch S. Reproduction control in cats: new developments in non-surgical methods. J Feline Med Surg. 2010 12:539-46
5. Groppetti D, Pecile A, Arrighi S, et al. Endometrial cytology and computerized morphometric analysis of epithelial nuclei: a useful tool for reproductive diagnosis in the bitch. Theriogenology 2010;73:927-941.
6. Klopfleisch R, Klose P, Gruber AD. The combined expression pattern of BMP2, LTBP4, and DERL1 discriminates malignant from benign canine mammary tumors. Veterinary Pathology 2010;47:446-454.
7. Millanta F, Caneschi V, Ressel L, et al. Expression of vascular endothelial growth factor in canine inflammatory and non-inflammatory mammary carcinoma. Journal of Comparative Pathology 2010;142:36-42.
8. Queiroga FL, Perez-Alenza D, Silvan G, et al. Serum and intratumoural GH and IGF-I concentrations: prognostic factors in the outcome of canine mammary cancer. Research in Veterinary Science 2010;89:396-403.
9. Renggli M, Padrutt I, Michel E, et al. Benign prostatic hyperplasia: treatment options in the dog. Schweizer Archiv fur Tierheilkunde 2010;152:279-284.