Veterinary Medicine - February 2008 - (Page 106) Hyperadrenocorticism and trilostane PEER-REVIEWED TABLE 1 TABLE 2 Clinical Signs of Hyperadrenocorticism Increased thirst and urination Increased appetite Abdominal distention Panting Muscle wasting and weakness Plantigrade stance Thinning skin Comedones Calcinosis cutis Pyoderma Truncal alopecia Laboratory Abnormalities Associated with Hyperadrenocorticism Serum chemistry profile Increased alkaline phosphatase activity Increased alanine transaminase activity (generally < twice the upper end of the normal range) Increased triglyceride concentration Increased cholesterol concentration Decreased blood urea nitrogen concentration Complete blood count Mild polycythemia (PCV 45% to 55%) Mature neutrophilia Lymphocytopenia Thrombocytosis Urinalysis Specific gravity 22 µg/dl is consistent with hyperadrenocorticism. • A post-stimulation cortisol concentration < 15 µg/dl is not supportive of hyperadrenocorticism. Note: • 20% to 30% of patients with hyperadrenocorticism stimulate below 22 µg/dl. • Nonadrenal disease can elevate the post-stimulation cortisol concentration. • The results of an ACTH stimulation test must be reviewed in light of other findings. *Source: Behrend EN, Kemppainen RJ, Bruyette DS, et al. Intramuscular administration of a low dose of ACTH for ACTH stimulation testing in dogs. J Am Vet Med Assoc 2006;229(4):528-530. Diagnosis In patients with the clinical signs of hyperadrenocorticism (Table 1) and supportive ndings on routine laboratory tests (Table 2), the diagnosis must be conrmed before therapy is considered. The two screening tests commonly used to diagnose hyperadrenocorticism are the ACTH stimulation test and the low-dose dexamethasone suppression test. The ACTH stimulation test (Table 3)1 is quicker and requires less venipuncture, but it may be less sensitive than the low-dose dexamethasone suppression test is.2 However, it is the only way to identify a patient with iatrogenic hyperadrenocorticism, and it provides information for post-treatment comparisons. The advantage of the low-dose dexamethasone suppression test (Table 4) is its potential for differentiating PDH from adrenocortical tumors.3 It is important to determine whether a patient has PDH or an adrenocortical tumor. The easiest way to answer this question is by performing an abdominal ultrasonographic examination. A competent scanner can easily identify both adrenal glands and assess their size and shape. Bilaterally normal or enlarged glands support PDH; asymmetry with a mass on one gland and atrophy of the other gland indicates an adrenocortical tumor. Other 106 February 2008 VETERINARY MEDICINE
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