Hypothalamo-pituitary-adrenal function in patients on long-term adrenocorticotrophin therapy.

Abstract

Thirty-one patients with rheumatoid arthritis who had been treated with a single daily injection of ACTH for 1 to 14 years were investigated. The integrity of their hypothalamo-pltuitary-adrenal (HPA) axis, using the Synacthen, Vasopressin, and insulin-hypoglycemia tests, and their response to acute withdrawal of ACTH were assessed. The group showed an increased adrenal responsiveness to Synacthen compared to the normal but an apparently diminished response to Vasopressin. The ability to produce a normal plasma cortisol in the withdrawal tests shown by all except 1 patient and the normal response to stress seen in the majority indicates that there is less risk of severe HPA suppression after long-term ACTH therapy than after oral corticosteroids. This may be due to the intermittent nature of the adrenal stimulation which is provided by a single daily dose of ACTH demonstrated by the studies of diurnal variation of cortisol in these patients.