A study of hypothalamic-pituitary-adrenal suppression following curative surgery for Cushing's syndrome due to adrenal adenoma

The hypothalamic-pituitary-adrenal axis was investigated in all six patients requiring glucocorticoid replacement 2.5-11 years after unilateral adrenalectomy for adrenal adenomas causing Cushing's syndrome. The hypothalamic-pituitary-adrenal axis was assessed by insulin induced hypoglycaemia and CRF testing in each patient. Two patients showed normal cortisol and ACTH responses to hypoglycaemia. Two patients showed subnormal cortisol responses to hypoglycaemia in the presence of high or normal basal ACTH concentrations. ACTH concentrations increased with both hypoglycaemia and CRF. Two patients showed subnormal cortisol responses to hypoglycaemia and CRF. One of these patients showed an ACTH rise following hypoglycaemia but not CRF. Defects at either hypothalamic-pituitary or adrenal levels were demonstrated and recovery of the axis appears to commence at the hypothalamic-pituitary level.