Monkey Breasts Provide a Clue
The male hormones have been known to improve sex drive and give us more lean body mass relative to fat mass, but can they cause breast cancer, or alternatively protect us from breast cancer? Petri dish studies and rat studies seem to indicate that if estrogen causes breast cells to grow, testosterone does the opposite. But what do the studies in real women say?
As with many hormone studies the actual epidemiologic studies have tended to report that perhaps there is a link between breast cancer and estrogen. and one study showed breast cancer relapse is higher if you have higher testosterone levels. Suthers writing in 2007 about how that Estratest is not approved by the FDA for sexual function found a two and half times greater risk of breast cancer in women who had used this compound vs never users of hormones and was also greater than women using hormone therapies that didn't have testosterone. And Suthers went on to quesion whether that type of testosterone could actually augment the effects of estrogen on breast cancer. So bring in the monkeys......
In the newest monkey study done in the Wake Forrest Monkey colony and funded by the NIH they exposed the monkeys and took biopsies to look at tissue effects. They were able to find that the cells of the lobes of the breast did proliferate and they did not find that testosterone specifically counteracted any of the effects of estrogen and progesterone. They thought that clinically, short term effects of testosterone on the female breast would be minimal.