The Assessment of the Functional Capacity of the Hypothalamic-Pituitary-Adrenal Axis by Measurement of Basal Plasma and Urinary Cortisol in Comparison With Insulin-Induced Hypoglycaemia and Metyrapone Tests

In 58 patients with a pituitary adenoma or hypothalamic-pituitary disease an insulin-induced hypoglycaemia test and a metyrapone test were performed. The results of these tests were compared with morning plasma cortisol levels and daily urinary cortisol excretion as indicators of insufficiency of the pituitary-adrenal axis. Basal unstressed urinary cortisol excretion was insufficient in 20 cases. These patients, needing life-long glucocorticoid substitution therapy, were excellently detected by both tests and daily urinary cortisol excretion. The predictive value of the morning plasma cortisol level was inferior to these. Five cases with sufficient basal cortisol excretion showed a defective adrenal response to hypoglycaemia. These patients were not discriminated by the metyrapone test, urinary cortisol excretion or plasma cortisol levels. It is concluded that urinary cortisol excretion can safely replace the hypoglycaemia and metyrapone test for the detection of insufficient basal cortisol production in patients with hypothalamic and/or pituitary disorders