Hypothalamic-pituitary-adrenal function in patients treated with long-term depot tetracosactrin

Four patients treated with depot tetracosactrin for 10 to 18 months maintained normal hypothalamic-pituitary-adrenal function assessed by the nyctohemeral variation of plasma corticosteroids and by the responses of plasma corticosteroids to insulin-induced hypoglycaemia, lysine-vasopressin, and depot tetracosactrin. The pituitary component of the response was analysed by measuring plasma immunoreactive ACTH levels. Three patients showed a nyctohemeral ACTH rhythm and normal ACTH responses to insulin-induced hypoglycaemia. Consistently undetectable morning plasma ACTH levels were found in the fourth patient, who also showed an unusually delayed rise in both ACTH and corticosteroid levels in response to insulin-induced hypoglycaemia, though the peak values attained were normal.The lack of suppression of hypothalamic-pituitary-adrenal function together with the good clinical response in these four patients suggests that treatment with depot tetracosactrin should be considered when long-term corticosteroid therapy is required.