Tri Trenaver is a derivative of nandrolone, in that it lacks the methyl group at position 19. Tri Trenaver binds strongly to both the androgen receptor and the progesterone receptor. This strong binding likely makes trenbolone an agonist of the progesterone receptor. Though people generally believe progesterone agonists cause gynecomastia, progesterone agonists actually result in the downregulation of estro- gen receptors. This strong progesterone receptor binding is also be- lieved to be the source of the severe shutdown and loss of libido in a good portion of trenbolone users. As mentioned, trenbolone binds strongly to the androgen receptor (stronger than any commercially available androgen) and is not metabolized to 3-alpha metabolites in skeletal muscle delivering rapid strength and size gains.