<unk>  (often referred to as<unk>  is an anabolic steroid. It has affinity to the androgen receptor and the progesterone receptor, but not to the estrogen receptor. The drug 
has been considered a "designer drug", closely related to the banned anabolic steroids gestrinone and trenbolone, and was banned by the Food and Drug Administration (FDA) at the end of 2003.
It was created by Patrick Arnold.
Anecdotal sources and some unpublished SAR studies report that the potency of the drug is outstanding, surpassing, on a milligram per milligram basis, every known synthesized or commercial available anabolic steroid. It was the drug of choice for safe and "invisible" world record breaking in athletics.
The drug was again made public when the United States Anti-Doping Agency was contacted by an anonymous athletics coach, later identified as Trevor Graham, who claimed that several top athletes were using<unk>  and provided the USADA with a syringe containing<unk> , which the USADA then used to develop a test for the substance.
The USADA identified the Bay Area Laboratory Co-operative (BALCO), an American nutritional supplement company, as the source of<unk> . The company manufactured the drug through palladium-charcoal catalyzed hydrogenation from gestrinone, a substance used in gynecology for treatment of endometriosis.<unk>  had been distributed to several leading athletes, including many during the BALCO scandal.
Tetrahydrogestrinone
Leuprolide
Nomegestrol
Ritiometan
Medroxyprogesterone acetate 
Gestodene
Hydroxyprogesterone caproate
Formestane