Tetrahydrogestrinone (often referred to as THG or "the clear") is an anabolic steroid. It has affinity to the androgen receptor and the progesterone receptor, but not to the estrogen receptor.Death AK, McGrath KC, Kazlauskas R, Handelsman DJ. Tetrahydrogestrinone is a potent androgen and progestin. J Clin Endocrinol Metab. 2004 May;89(5):2498-500^* The drug has been considered a "designer drug", closely related to the banned anabolica gestrinone and trenbolone.Oct.2003 FDA statement on THG, and was banned by the Food and Drug Administration (FDA) at the end of 2003.THG ban

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 THG. The same coach subsequently provided the USADA with a syringe containing THG, which the USADA then used to develop a test for the substance.

The USADA identified the Bay Area Laboratory Co-operative, an American nutritional supplement company, as the source of THG. The company manufactured the drug through palladium-charcoal catalyzed hydrogenation from gestrinone, a substance used in gynecology for treatment of endometriosis. THG had been distributed to several athletes by trainer Greg Anderson, who only identified it to athletes as "the clear". He provided it in conjunction with "the cream", a testosterone based topical cream. British 100m sprinter Dwain Chambers is a known athlete to have been caught with possession of the drug in his blood. He received a two year ban from running and a full life ban from the Olympic Games.

References