Estrogen Metabolism in the Human. II. Studies in the Male Using Estradiol-17β-6,7-3H

Abstract

Estradiol-17β-6,7-³H was administered to a group of normal male subjects. The urinary excretion of radioactive conjugated estrone, estradiol-17β and estriol was estimated, together with the simultaneous excretion of the corresponding endogenous (nonradioactive) estrogens. Specific activities were determined, and estradiol-17β production rates were calculated. A previously described mathematical model was used in analyzing the results. All results were compared with those in a previous study in males using estrone-6,7-³H. The mean urinary excretion of radioactive conjugated estrone, estradiol-17β and estriol was (% of administered dose, sd in parentheses): 9.33 (3.06), 3.87 (1.13), 6.87 (2.25). The value for radioactive conjugated urinary estradiol-17β was significantly higher, and that for radioactive conjugated urinary estriol was significantly lower, respectively, than those obtained following estrone-6,7-³H administration. The relationship of specific activities was also significantly different. The mean estradiol-17β production rate was 29.0 μg/day, SD 14.3, which was significantly lower than the estrone production rate previously determined. Fitting of the data to the mathematical model yielded results which were not consistent with the hypothesis that urinary estrone, estradiol-17β and estriol conjugates are derived solely from secreted estradiol-17β. Further analysis suggested that in males the secretion and metabolism of estrone and estradiol-17β may not be adequately described by a chemical “2-compartment” system.