EFFECT OF GLUCOCORTICOIDS ON PLASMA TESTOSTERONE IN MEN

Abstract

ACTH decreases plasma testosterone levels in men. The part played by the glucocorticoids in this effect, and the mechanism of their action was investigated. Plasma androstenedione, testosterone, cortisol and LH [lutropin] were measured in 8 normal men, before and after the following tests: ACTH stimulation (2 mg i.m.), metyrapone administration (500 mg/every 4 h, 6 times) and dexamethasone suppression (8 mg/day, 3 days). In addition, androstenedione and testosterone were evaluated under human chorionic gonadotropin (5000 IU hCG/day, 3 days) before and after dexamethasone suppression (8 mg/day, 6 days). In all patients, ACTH decreased plasma testosterone from 5.87 .+-. 1.59 (SD) ng/ml to 3.06 .+-. 0.8 (SD) ng/ml (P < 0.001). After metyrapone, the mean plasma testosterone was increased to 6.98 .+-. 1.75 (SD) ng/ml. This increase, though not statistically significant, was observed in all patients but one. Both tests resulted in a significant increase of plasma androstenedione (P < 0.01 and P < 0.001, respectively). Dexamethasone suppressed both testosterone and androstenedione levels. None of the 3 tests had a significant effect on the LH concentration. Injection of hCG increased the mean plasma testosterone to 11.46 .+-. 2.80 ng/ml. Dexamethasone significantly depressed (P < 0.01) the testosterone response to hCG. The decrease of plasma testosterone levels, observed in men after ACTH administration, is not observed after metyrapone induced ACTH increase. This may confirm that it is related to cortisol levels rather than to ACTH itself. Glucocorticoids apparently act directly on testicular biosynthesis since they do not induce any change in LH secretion and since dexamethasone reduced testosterone response to hCG.