Plasma Ketosteroids and Testosterone in Man: A Study of the Pituitary-testicular Axis*

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Abstract
A double isotope derivative method using gas-liquid chromatography is presented for the simultaneous measurement of unconjugated testosterone, lehydroepiandrosterone, androsterone, and eticholanolone in plasma of man. Plasma dehydroepiandrosterone levels showed a diurnal variation with a 26% decrease from morning to afternoon. No such changes were noted in plasma testosterone levels. Plasma testosterone levels increased 2 to 6 hr. after chorionic gonadotropin and were suppressed 50% with physiologic doses of exogenous androgens. This suppression was even more marked with higher doses. The similarities of the relationship of the Leydig cell to the anterior pituitary gland with the adrenal cortical-anterior pituitary axis have been pointed out. The contribuiton of adrenal secretions to plasma testosterone and dehydroepiandrosterone levels in man was measured. Prednisone administration markedly lowered the plasma dehydroepiandrosterone level, but resulted in only a 21% decrease of plasma testosterone.