Estrogen receptors in male gynecomastia.

Nineteen tissue specimens obtained at surgery of male mammary gland due to persisting gynecomastia were assessed for the presence of estrogen receptors. In 13 cases the receptors were detected with the use of charcoal-dextran technique and 3H-estradiol as a ligand, the detection limit of such method being 0.2 fmol/mg of total protein. The average number of estrogen binding sites (mean +/- S. D.) was 2.49 +/- 2.47 fmol/mg total protein with the apparent association constant 2.8 X 10(9) 1 mol-1. The specificity of ligand binding to the receptor was confirmed by gradient centrifugation.