Monkey Breasts Provide a Clue

Actually it was a study of cynomolguss monkey breasts. The whole question has been, as women age, and loose estrogen, and loose progesterone, and even eventually drop their testosterone levels what effects does this have on our tissues. For a time we are "androgen dominant" meaning only weak circulating estrogens, and still producing some male hormones. Although we can look a our patient's levels and see if her hormones on spot checks fall out of the normal ranges, and we can look at trends of hormone levels over time. There is still not an agreed upon method to make a formal diagnosis of male hormone (androgen) deficiency.

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.


  1. What would be the effect in women with polycystic ovary disorder both before and after menopause?

  2. The effects of estrogen and testosterone in women with PCOS can be complex, whether it is before menopause or after menopause. Many of these women are very estrogen dominant; others have excessive amounts of male hormone. After menopause PCOS should theoretically abate if the cause was the abnormal production of hormones in the ovary. How the abnormal levels of estrogen and testosterone of premenopausal women would affect the breast in the long run, or whether that would affect hormone therapy, is, as far as I know, largely unstudied. This topic would make a great topic for future research. Thanks.


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