Some cases of gynecomastia arise naturally, often when hormonal balances are shifted during puberty or later in life when endogenous production of androgens decreases (andropause).

However, a very common cause of gynecomastia is the use of anabolic steroids by bodybuilders. When external sources of testosterone are introduced, the body reduces its own natural production of testosterone in response. Naturally, when the external source of testosterone is removed, the body now has a shortage of androgens and the androgen-estrogen balance swings in favor of the female hormones.

In men, the natural state is generally a dominance of androgens. With an estrogen-dominant scenario, the body is in a state similar to female puberty, and the mechanisms that cause development of breast tissue are triggered. Both men and women have the genetic capability for breast development; in men it is just usually not unlocked.

As well, when there is a significant excess of testosterone in the body, as occurs with steroid use, the body clears this excess by converting some of the excess androgens to estrogens through the function of aromitase. This contributes to the estrogen dominance that occurs when external testosterone is removed.

It is for this reason that bodybuilders using steroids are often advised to use estrogen inhibitors when they come off a cycle of added testosterone. Even a short cycle of a relatively mild androgen supplement like M1T have the potential to induce gynecomastia, and the potential increases with longer cycles of more potent supplements.

Recommended estrogen inhibitors can vary from herbal remedies to (probably illegal) breast cancer medications such as Nolvadex (Tamoxifen) or Letrozole, which are designed to interfere with the body’s ability to produce or utilize estrogens. If you were able to get your hands on steroids in the first place, you’ll probably be able to hunt down the estrogen inhibitors as well.

This is the manner in which steroid use can result in gynecomastia. Its ramifications are discussed further in GYNECOMASTIA AND BODYBUILDERS.