Steroid biosynthetic potential of gynaecomastic tissue in man.

In vitro transformation of precursors to androgens and oestrogens was studied in breast tissues from 7 phenotypic males with gynaecomastia and 3 normal females. All the tissues studied showed formation of dihydrotestosterone and oestrogens, thus demonstrating the presence of 5alpha-reductase and aromatizing enzymes. The results on the values of urinary oestrogens before and after surgical removal of the breast tissue substantiate the biosynthetic potential of gynaecomastic tissue. The aetiological significance of these findings vis-à-vis gynaecomastia is discussed.