δ4-Tibolone (developmental code ORG-OM-38; also known as isotibolone, 7α-methylnorethisterone, or 7α-methyl-17α-ethynyl-19-nortestosterone) is a synthetic androgen and progestin which was never marketed. The compound is a major active metabolite of tibolone, which itself is a prodrug of δ4-tibolone along with 3α-hydroxytibolone and 3β-hydroxytibolone (which, in contrast to δ4-tibolone, are estrogens). Tibolone and δ4-tibolone are thought to be responsible for the androgenic and progestogenic activity of tibolone, while 3α-hydroxytibolone and 3β-hydroxytibolone are thought to be responsible for its estrogenic activity.
Activity Isotibolone exhibited both estrogenic and progestogenic properties in several biological test systems and was found to be 10 to 40 times as potent as norethindrone in comparative assays. Tested for androgenic activity, it stimulated growth of seminal vesicles and the levator ani but was relatively inactive in stimulating prostate gland growth.
See also List of androgens/anabolic steroids List of progestogens
References