THG Profile

by THG (tetrahydrogestrinone), often referred to as “The Clear”, is a potent anabolic and progestagenic androgenic steroid that is chemically and structurally related to two other synthetic anabolic steroids, gestrinone and trenbolone (1). The “designer steroid” was derived by simple chemical modification of another anabolic steroid that is explicitly banned by the the World Anti-Doping Agency (WADA).

Chemist Patrick Arnold, the “father of prohormones” in the U.S. sports nutrition market, is credited with the creating THG via the catalytic hydrogenation of gestrinone to evade detection. Patrick Arnold along with Victor Conte of the Bay Area Laboratory Co-operative (BALCO) were identified as the source of THG which was distributed to several top athletics in various sports in the American and European athletic scenes. Unlike other anabolic-androgenic steroids used illicitly by competitive athletes, which were pharmaceuticals intended for veterinarian or human use, THG had never been approved for any medical indication nor introduced into commerce.

THG remained undetectable by sport doping control urine tests for several years. This changed in the summer of 2003 when Don Catlin director of the IOC/WADA accredited laboratory in Los Angeles was mailed a sample of a substance by an anonymous track coach (later identified as Trevor Graham) that enabled the structure of THG to be determined and a detection methodology to be developed (2).

THG has since been prohibited both in and out of competition under the World Anti-Doping Code. The protocol for THG detection is used by IOC / WADA accredited laboratories throughout the world for sample analysis.

The use of tetrahydrogestrinone (THG) by several elite athletes led the US Congress to add it to the Anabolic Steroid Control Act of 2004 as a “Schedule III” controlled substance. THG, although pharmacologically defined as an anabolic-androgenic steroid, was legally defined as an “unapproved new drug” during its role in the BALCO scandal.


  1. 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
  2. Catlin D. H., Sekera M. H., Ahrens B. D., Starcevic B., Chang Y. C., Hatton C. K. Tetrahydrogestrinone: discovery, synthesis, and detection in urine. Rapid Commun Mass Spectrom. 2004;18:1245–049.
  3. Yu-Chen Chang; Borislav Starcevic; Brian D. Ahrens; M. Jane Strouse; Don H. Catlin. Identification of a Urinary Metabolite of the Designer Steroid Tetrahydrogestrinone (THG). Drug Metab: Toxicology.