PITUITARY-FUNCTION TESTS - COMPARISON OF ACTH AND 11-DEOXY-CORTISOL RESPONSES IN THE METYRAPONE TEST AND WITH THE INSULIN HYPOGLYCEMIA TEST

Purpose: To compare the sensitivity of ACTH and 11-deoxy-cortisol (com p. S) responses in the short metyrapone test and the latter with the i nsulin hypoglycemia test. Methods: Retrospective evaluation of 115 sho rt metyrapone tests and comparison of 18 pairs of metyrapone and insul in tests. 20 healthy controls and 95 patients with confirmed pituitary disease were studied. All hormones were measured by sensitive radioim munoassays. Results: In patients with pituitary disease not requiring hydrocortisone substitution (n = 70), the ACTH response in the metyrap one test was subnormal in 47 cases (< 33 pmol/L), the comp. S response (< 200 nmol/L) in 21 cases only. Comparison of the relationship betwe en ACTH and comp. S with an ACTH-cortisol dose-response curve obtained in normal subjects shows that subnormal ACTH responses after metyrapo ne in the range between 13 and 33 pmol/L still generate normal comp. S responses. The results of the metyrapone test correlated significantl y with those of the insulin test. Conclusions: Measuring plasma ACTH i n the scope of the metyrapone test makes the lest more sensitive to de tect secondary adrenal insufficiency than with steroid measurements al one. Results of the metyrapone test correlate significantly with the c ortisol response to insulin hypoglycemia.