Evaluation of serum concentrations of cortisol and sex hormones of adrenal gland origin after stimulation with two synthetic ACTH preparations in clinically normal dogs.

OBJECTIVE: To compare the adrenocortical response of healthy dogs to a commonly used dose of a nonadsorbed tetracosactide product (tetracosactide) with responses to 2 doses of a depot formulation of tetracosactide (depot tetracosactide). ANIMALS: 14 dogs. PROCEDURES: Dogs were randomly assigned to receive tetracosactide (5 mg/kg, IV) or depot tetracosactide (250 µg, IM, or 5 µg/kg, IM). Dogs received each treatment once with a 2-week interval between treatments. Blood samples were assayed for cortisol, progesterone, 17-hydroxyprogesterone, androstenedione, and estradiol concentrations. RESULTS: Serum cortisol concentrations were significantly higher than the preadministration (baseline) concentrations for all treatments 60 minutes after administration of ACTH. Peak cortisol concentration was detected 180 minutes after IM administration of 250 µg of the depot tetracosactide. Serum concentrations of progesterone, 17-hydroxyprogesterone, and androstenedione did not differ significantly from baseline concentrations after stimulation with the 5 µg/kg dose of depot tetracosactide. Adrenal gland progesterone response was significantly higher than baseline concentrations at 60 minutes after administration of the 250-µg dose of depot tetracosactide, and the 17-hydroxyprogesterone and androstenedione responses were significantly higher than baseline concentrations at 120 minutes. Compared with the response to tetracosactide, adrenocortical response was higher and more sustained following administration of the depot tetracosactide, except for androstenedione concentration, which had a nonsignificant response. CONCLUSIONS AND CLINICAL RELEVANCE: Except for androstenedione concentrations, a high dose of the depot tetracosactide (250 µg, IM) induced an adrenocortical response similar to that after administration of tetracosactide. Thus, depot tetracosactide may represent an alternative to the nonadsorbed tetracosactide product.