Part of “CHAPTER 120 – GYNECOMASTIA“

Given the long-recognized role of estrogens in stimulating mammary growth, it is not surprising that high circulating estrogen levels of exogenous or endogenous origin can be associated with gynecomastia. More recently, however, gynecomastia has been noted in disorders with deficient androgen production even when estrogen production is normal, leading to the concept that gynecomastia often may be related to increases in the circulating estrogen/androgen ratio rather than to absolute increases in estrogen per se. Finally, the occurrence of gynecomastia in conditions in which the androgen sensitivity of peripheral target tissues is reduced, even without significant changes in circulating androgens or estrogens, has refined this concept to suggest that gynecomastia is related to the resultant estrogen/androgen ratio effect at the breast. Although experimental evidence is inconclusive, this has proved to be a useful framework for evaluating gynecomastia.