Adrenal Response to Infused Corticotropin in Subjects Receiving Glucocorticoids

Abstract

Adrenocortical function has been studied by determining the plasma 17-hydroxycorticosteroid response to maximum stimulation with intravenously infused corticotropin. Fifty patients who had received glucocorticoid therapy for 12 to 100 months all showed a diminished response as compared with 58 control subjects. The degree of impairment was related to both the dose and the duration of steroid therapy. Thus, patients receiving 10 or more mg of prednisolone daily (or the equivalent dose of other glucocorticoids) showed a significantly smaller plasma corticosteroid rise during the infusion of corticotropin than patients receiving 5 or 7.5 mg daily. Amounts in excess of 15 mg daily caused maximal adrenal suppression. Adrenal responsiveness was significantly impaired after only 5 days of prednisolone therapy (20 mg daily). The infusion of corticotropin (10 IU/hr) together with dexamethasone (1 mg/hr) increased the plasma corticosteroid concentration at the same rate as the infusion of corticotropin alone. Thus, with these doses, glucocorticoids did not directly affect adrenal function, and it was considered that the adrenal effects of glucocorticoid therapy were explicable in terms of inhibition of corticotropin release. In patients who had received prolonged glucocorticoid therapy, weekly intramuscular injections of 120 IU of a long-acting corticotropin gel preparation did not prevent adrenal impairment, but adrenal responsiveness was restored to normal by twice daily injections given for 4 days.