Page 147 - Clinical Small Animal Internal Medicine

14 Canine Autoimmune Polyglandular Syndromes 115

in a patient with APS so starting once daily would be sug­ Conclusion
VetBooks.ir gested. When the hypothyroid and hypoadrenal states In summary, multiple endocrine deficiencies occur with a
occur concurrently, the rate of clearance of cortisol and
cholesterol is reduced due to low serum thyroxine con­
centrations. When thyroid supplementation is initiated, low incidence in dogs with hypoadrenocorticism, hypo­
thyroidism, IDDM, and perhaps hypoparathyroidism.
cortisol clearance increases suddenly without a compen­ This syndrome appears to be similar to APS 2 of human
satory increase in cortisol synthesis because of destruc­ beings. Veterinarians should be aware of some of the fea­
tion of adrenal tissue. As a result, thyroid therapy may tures, such as persistent hyponatremia and hypercholes­
precipitate an adrenal crisis. Hence, one should assess terolemia, which may indicate the presence of multiple
adrenal function prior to initiation of levothyroxine ther­ endocrinopathies in the same individual. Dogs with
apy in animals with suspected multiple endocrinopa­ hypoadrenocorticism that exhibit inadequate response to
thies. In dogs with diabetes mellitus and hypothyroidism, therapy, persistent hypercholesterolemia and hypona­
one must balance the insulin dose with the levothyroxine tremia despite normalization of serum potassium, derma­
therapy. A reduction of 25% of the insulin dose is recom­ tologic disease, and/or bradycardia should be evaluated
mended when starting levothyroxine at 22 μg/kg BID. In for thyroid function. Diabetic dogs that exhibit inadequate
dogs with hypoadrenocorticism and diabetes mellitus, glycemic control associated with persistent hyponatremia,
the insulin dose will need to be gradually increased as hypercholesterolemia (>500 mg/dL), obesity and derma­
supplementation with glucocorticoids (0.22 mg/kg PO tologic disease should also be tested for hypothyroidism.
q24h) and DOCP will cause insulin resistance.

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