Estrogen blockers are supplements that reduce the production of estrogen and effects of estrogen on the body. Estrogen blockers restore the hormone balance where the testosterone levels may be low and high estrogen levels and where high levels of testosterone levels are present and some of this testosterone aromitizes or converts to estrogen what may lead to water retention, bloating, fat gain, breast tissue enlargement (bitch tits) which is not great if you are a man, further more it also may cause sexual/erectile dysfunction, low energy and inability to increase the muscle mass. It’s also worth to mention that fat cells are an active participant in endocrinology – hormone balance – and the part of this is turning testosterone to estrogen. In other words, the more fat cells you have, the more testosterone converts to estrogen. But eliminating your estrogen down to nothing is not the answer and that would lead to other problems as well. The answer is to keep testosterone and estrogen at optimal levels. Sports supplements work the way that they help body metabolize and eliminate estrogen from circulation as opposed to medication that blocks the enzyme aromatase from converting testosterone to estrogen.