Introduction Benign breast enlargement in males secondary to increased effective estrogen can be increased production or decreased degradation also result of decrease in androgens leaving estrogens unopposed May occur naturally throughout male life newborn secondary to high maternal estrogen puberty elderly secondary to androgen decrease Associated conditions cirrhosis genetic diseases Klinefelter syndrome increased aromatizing activity of Leydig cells high estrogen results in increased male breast cancer risk testicular feminization cancer choriocarcinoma of testis high production of hCG (an LH analogue) drugs estrogen marijuana flutamide blocks androgen receptors leuprolide blocks androgen production psychoactive drugs "Some Drugs Create Awesome Knockers" Spironolactone block androgen receptors, displaces estrogen from SHBG Digitalis intrinsic estrogen activity Cimetidine Alcohol Ketoconazole displaces estrogen from SHBG