Studies of the Metabolism of 17α-Estradiol in Man1

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Abstract
When 50 mg of 17[alpha]-estradiol was given orally to each of 2 male subjects, estrone was isolated as metabolite from the urine; only trace amounts, at most, of 17[beta]-estradiol could be detected. Of the total dose of 17[alpha]-estradiol administered, only 2.2 and 3.4%, respectively, were recovered in the estrone, estradiol and estriol fractions, as determined by the method of Brown, Bulbrook and Greenwood (4). to comparative experiments with 17[beta]-estradiol, 20% of the administered dose was recovered. Similarly, 17a-estradiol was metabolized to a greater extent than 17[beta]-estradiol during incubation with human liver slices. The results obtained show that a 17[alpha]-hydroxysteroid oxidoreductase is present in man and that the metabolism of 17[alpha]-estradiol in vivo as well as in vitro differs from that of 17[beta]-estradiol.