Friday, February 4, 2011

Q & A: Hypercalcemia in a Dog with Addison's Disease?

"Molly" is a 5-year-old Westie who was diagnosed with hypoadrenocorticism 3 years ago.  She has been getting DOCP (Percorten) injections every 3 to 4 weeks since that time.  She has been remarkably easy to regulate and very stable. She only takes prednisone as needed for stressful times (eg, boarding or grooming).  

The owners have been complaining of polyuria and polydispia (PU/PD) almost since the start of her treatment for Addison's disease, but lately they feel it is worse.  There has been no vomiting or diarrhea, and the dog appears normal in all other respects. 

We did a serum chemistry profile and, although the serum sodium and potassium concentrations were normal, her calcium was mildly high. The pertinent results are listed below:

     Potassium = 4.1  mEq/L (reference range, 3.7-5.8 mEq/L)

     Sodium = 143  mEq/L (reference range, 138-160 mEq/L)

     Calcium = 12.3 mg/dl (reference range, 8.6-11.8 mg/dl)

     Albumin= 4.1  mg/dl (reference range, 2.5-4.4 mg/dl)
     Urine specific gravity = 1.012
     Urine culture - negative

My questions: Molly has not had an high serum calcium level in the past. Is the mild hypercalcemia a concern at this point?  Should we consider changing her dose?  Right now she is taking 2 mg/kg of the Percorten IM every 3 - 4 weeks.  Would it be better to consider changing her to oral Florinef? Should I pursue running an ionized calcium or a PTH level?  

The owners are stretched financially just paying for the DOCP injections.  I am not sure how much more they will pay if I can't give them a really good reason for more tests.  

Thank you for your advice.

My Response:

The Addison's disease is NOT causing the hypercalcemia at this point. We only see that in unregulated patients (who generally are in adrenal crisis). In contrast, this dog appears to be very stable. The dog's PU/PD could be related to the hypercalcemia since she isn't on daily glucocorticoids. However, I'd also seen PU/PD develop secondary to the Percorten treatment.

I'd repeat the serum calcium at some point in the relatively near future (2-3 weeks). If the total calcium remains high at that point, I'd verify the hypercalcemia with a ionized calcium and get a PTH value. If the ionized calcium is normal, then the hypercalcemia may not be anything to worry about.

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