Deca and Tren induced gyno caused by Prolactin.
http://www.anasci.org/vB/anabolic-steroid-discussion-board/2304-thinking-about-doing-steroids-read.html
Im not sure how to quote stuff but this link is to a page that has this on it.
The Cycle - Anti-estrogens
An anti-estrogen (usually Nolvadex or Arimidex) will need to be purchsed to have handy in case gyno symptoms start. Itchy and sore nipples will tell you that you are getting gyno, and Nolvadex should be started (I use Nolva personally so I am showing Nolva dosages) at 60mg per day for 2 days, then 40 for one day, then 20mg for the rest of the cycle. There is one catch tho.... Nolvadex and Arimidex will only take care of estrogen driven Gyno...... Gyno that is caused by prolactin needs to be countered by using proviron. Prolactin induced gyno can occur from Trenbolone or Deca.
There is also Cabergoline (brand names Dostinex and Cabaser), or
bromocriptine. I have only done a cycle in high school and it was completely incorrect so I am no authority on this, but through research on this page and doing my own research this is what i have found. If i am incorrect some one please correct me for my knowledge as well as others.