Adrenal insufficiency associated with long-term anabolic steroid administration in a horse

Adrenal insufficiency was diagnosed in a 9-year-old American Quarter Horse gelding that had received monthly injections of stanozolol for 8 years. After the injections were abruptly discontinued, the horse developed anorexia, lethargy, weight loss, and bilateral forelimb lameness. Secondary hypoadrenocorticism was diagnosed on the basis of clinical signs, lack of high endogenous plasma ACTH concentration, and lack of cortisol response to administration of ACTH. Because the medical history did not include glucocorticoid administration, the cause was determined to be excessive administration of an anabolic steroid. Treatment consisted of physiologic glucocorticoid replacement for 9 months until adrenal function returned. Findings in this horse indicate that anabolic steroids influence the hypothalamic-pituitary axis in horses.