Natural History of Pituitary-Adrenal Recovery Following Long-Term Suppression with Corticosteroids

Plasma ACTH and 17-hydroxycorticosteroid concentrations were measured at various intervals in patients recovering from prolonged pituitary suppression. Pituitary-adrenal recovery was found to follow a definite pattern requiring several months for completion. Initially, both ACTH and corticosteroid levels were relatively low, a situation similar to that seen in patients with hypopituitarism. Thereafter, plasma ACTH levels gradually increased until they were supernormal, but there was a lag of several months in the recovery of normal adrenal responsiveness. Despite the fact that the pituitary gland could secrete large quantities of ACTH and despite the fact that corticosteroid levels were subnormal, a diurnal rhythm was observed in ACTH levels with a decrease to low values during the latter portion of each day. After several months, corticosteroid levels rose to normal, and soon thereafter plasma ACTH concentrations fell again to normal.