Plasma Immunoreactive Corticotrophin and Cortisol Response to Insulin Hypoglycemia in Normal Subjects and Patients with Pituitary Disease

The blood sugar, plasma cortisol and immunoreactive corticotrophin (ACTH) responses to insulin-induced hypoglycemia were analyzed in detail in 9 individuals without evidence of pituitary disease and 6 patients with hypopituitarism. In all the control subjects, plasma ACTH levels more than trebled to reach a maximum 45 min after the insulin injection. The maximum cortisol response occurred 15–45 min after the ACTH peak and was more prolonged. However, the magnitude of the ACTH response, relative to resting levels, was greater. The above time-response relationships may be altered in Cushing's disease and in patients taking adrenal steroids. In patients with hypopituitarism, the magnitude of the cortisol and ACTH responses was greatly reduced. The rise in blood sugar levels after the blood sugar nadir was significantly delayed in these patients, but was an insensitive index of ACTH release. A more accurate assessment of pituitary-adrenal function was obtained if the maximum ACTH or cortisol level was used rather than the increment rise.