Trenbolone also has progestagenic affects. Tren, possesses strong androgenic properties. Tren is not known in the anabolic steroid community to cause gyno. However, many cycles of anabolic steroids which include a heavily aromatizing steroid with trenbolone. No doubt many combine tren and testosterone . Remember, progesterone sensitizes the body to estrogen, so whatever estrogen is available will be more likely to act out and cause the negative effects we know estrogen is responsible for. The moral of the story is to be cautious and knowledgeable about the drugs you are combining