Non-dexamethasone-suppressible, pituitary-dependent hyperadrenocorticism in a dog.
A 5-year-old female dog with hyperadrenocorticism was determined to have pituitary-dependent hyperadrenocorticism even though plasma cortisol concentrations were not suppressed after high-dosage dexamethasone administration. The diagnosis was based on a supranormal response of plasma cortisol to ACTH administration and a lack of suppression of plasma cortisol concentration after administration of 0.1 mg of dexamethasone/kg. Although a higher dosage of dexamethasone (1 mg/kg) did not cause suppression of plasma cortisol, plasma ACTH concentrations in the dog were increased above those in clinically normal dogs, supporting a diagnosis of pituitary-dependent hyperadrenocorticism. During treatment with mitotane, the dog became unconscious and died. Necropsy revealed a pituitary tumor that had compressed and displaced the hypothalamus. Although high-dosage dexamethasone suppression tests often are useful in the differential diagnosis of hyperadrenocorticism, a lack of suppression of plasma cortisol does not necessarily exclude pituitary-dependent hyperadrenocorticism.
D000238:Adenoma, Chromophobe / Q000150:complications / Q000175:diagnosis / Q000662:veterinary*; D000308:Adrenocortical Hyperfunction / Q000209:etiology / Q000662:veterinary*; D000818:Animals; D003907:Dexamethasone; D003937:Diagnosis, Differential; D004283:Dog Diseases / Q000175:diagnosis*; D004285:Dogs; D005260:Female; D010911:Pituitary Neoplasms / Q000150:complications / Q000175:diagnosis / Q000662:veterinary*
D003907:Dexamethasone