Progesterone Gyno

September 7th, 2007 by Paul Johnson

Bodybuilders have used Trenbolone and have found themselves developing gyno even though it doesn't convert to estrogen. Gyno, also known as gynecomastia ( male breast growth), is often considered to be the result of estrogen. However, Tren has the unique ability to cause gyno without actually producing estrogen.

Role of Progesterone in causing gyno:

Progesterone is found in both males and females. It is a precursor to many important hormones in men and women. In women it plays a role in pregnancy and in breast growth. In men, excessive progesterone can stimulate breast growth, like it does with women. While Estrogen is normally the cause of gynecomastia under normal physiological conditions, Tren and other similiar steroids stimulate the progesterone receptors because they are not only anabolic steroids, but also of a class called progestins. Progestins are the synthetic forms of steroids structurally similiar to progesterone, that have the ability to bind to the progesterone receptor too. Deca and Anadrol also are progestins, but they also aromotize to estrogen, unlike Tren. Some bodybuilders coin the term “progesterone gyno”, to explain gyno from progestin steroids.

Progesterone Gyno Controversy:

There is a major debate among bodybuilders on this entire topic. Some believe that progesterone causes the gyno in Tren users. Others believe it is actually prolactin, the hormone responsible for lactation and breast growth during a women's pregnancy. This may explain why some experience lactating on tren cycles. Others believe it is a combination of estrogens and either prolactin or progesterone, working all synergistically to develop gyno.

Who is right?

Many Research studies I've seen, show that estrogen plays a synergistic role with progesterone, prolactin, and in gynecomastia. Although some bodybuilders say it's the prolactin or progesterone directly causing it, there is no studies to show gyno can develop without high levels of estrogen. Even IGF-1 and Growth hormone has been shown in studies to play a crucial synergistic role in the development of breast tissue. So I believe no matter what kind of steroid you take, lowering estrogen with anti-estrogens and avoiding stacking Tren with aromatizing steroids, is how you really prevent "Progesterone gyno". With very low levels of circulating estrogen, it appears impossible or very difficult for progesterone gyno to develop.

  1. lee on April 1st, 2010

    alright been taking prohormones and went with one that i believed wouldnt cause gyno but was wrong(trenavol v) stopped taking after just 16 days because nipple region was puffy. taking novedex xt now. will this go away or will it get worse