Simplified Assessment of Pituitary-Adrenal Reserve

Abstract

The metyrapone test has been improved by specific measurement of plasma 11-deoxycortisol. This simplified method measures 11-deoxycortisol and cortisol in a sample of 0.1 ml of plasma after a standard dose of metyrapone. In normal patients, after metyrapone ingestion, plasma 11-deoxycortisol rises from a base line of 0.8 ± 0.8 µg/100 ml to 16.8 ± 4.4 µg/100 ml, and plasma cortisol falls from 13.5 ± 5.1 µg/100 ml to 3.3 ± 2.8 µg/100 ml. After metyrapone 11-deoxycortisol is reduced only in adrenocorticotrophin (ACTH) deficiency. Patients with hypopituitarism or chronic corticoid therapy and 9 of 12 acromegalics had subnormal levels. Patients with the "empty sella" syndrome or trophic hormone deficiency other than ACTH had normal levels. In primary hypothyroidism postmetyrapone 11-deoxycortisol is significantly greater than in normals. This difference is thought to be caused by delayed metabolic clearance of the steroid. Simultaneous measurement of serum cortisol affords an internal standard for the degree of 11-hydroxylation block achieved by the amount of administered metyrapone.