I do not consider trenbolone to be capable of causing or aggravating gynecomastia. I do not know of a single case where the source of trenbolone was Parabolan (back when it was available), Finaplix H, or Component T-H. The problem appears to occur only when the source is an underground lab or the home preparation is made from powder from a black-market supplier. Since trenbolone’s wholesale price direct from a manufacturer is much higher than that of most anabolic steroids , it shouldn’t be surprising that substitution or partial substitutiion would often occur with underground products. Additionally, it might be that some have mistakenly made preparations from Finaplix S, which definitely would be capable of causing gyno, as that product includes estradiol benzoate as an ingredient.