[A horse with Cushing's disease].

A thirteen-year-old Dutch warmblooded mare was referred to the Faculty of Veterinary Medicine because of a sinusitis. She was thin with a potbellied appearance. Her coat was dull with long wavy hair. Unilateral (left) purulent nasal discharge was evident. A cbc revealed leucopenia (3.9 G.L.-1) and plasma biochemical analysis revealed a plasma glucose concentration of 10.1 mmol.L-1. Thermostable alkaline phosphatase (at 65 degrees C during 2 minutes) could not be demonstrated. Basal plasma cortisol concentration was lowered (114 nmol.L-1) and basal plasma ACTH concentration was highly elevated (815 pg.ml-1), indicating adrenocortical insufficiency. A dexamethasone-suppression test was performed by intramuscular administering of 10 mg of dexamethasone showing a suppression of 32% instead of at least 50%. At necropsy a pituitary pars intermedia adenoma was found.