Estrogen synthesis in normal and hypogonadal men. Quantitative studies on the precursor role of testosterone.

Abstract

Tritiated (7α-3H) testosterone was injected intravenously into normal and hypogonadal men after which all urine was collected for 5 days. The urine was assayed for estrone, 17β-estradiol, estriol, and 3H associated with these fractions by the new method of Blair and co-workers. The specific activities of the urinary estrogen fractions from the normal men were sufficiently low to warrant the conclusion that there were other sources of estrogen production in addition to the plasma testosterone pool. It was also shown that the higher specific activities observed in this laboratory during a previous study, similar except that the Bauld method was used for the assays, were due to radiochemical impurities in the final estrogen fractions. The hypogonadal men had low urinary estrogen levels but there was no evidence of gross abnormality in the metabolism of 3H-testosterone to 3H-estrogens in this group.In two out of three instances, 1,2-3H-testosterone injection produced less 3H-labeled urinary estrogen than 7-3H-testosterone injection. This finding suggested that 3H was lost either from the C-1 or the C-2 position during the biosynthesis of estradiol from testosterone.