Most interesting was the discovery that cytochrome P450 aromatase, which is capable of converting androgens into estrogens, is present in the testis [25–39]. During this same period of discovery, others were using the radioim- munoassay to identify steroids present in body fluids and estrogen concentrations were found to be relatively high in seminal and rete testis plasma [40–48]. Thus, up to the 1990's it appears that most scientific inquiry into estro- gen's presence in the male remained a curiosity, as well as a worry that estrogen exposure during development was harmful. Then, in the decade of the 90's new discoveries in the male led to the hypothesis that estrogen not only has.
