THG or tetrahydrogestrinone is pharmacologically classified as an anabolic agent. Anabolic androgenic steroids include both natural present and synthetic substances which have an effect on the body similar to that of Testosterone.

THG has been labelled as a "designer" steroid as it would appear to have been specifically chemically synthesised to be undetectable using currently used drug testing methods.

It is not legitimately available or licensed for use as a medicine. While its full pharmacological effects have not been published or perhaps even fully studied, THG would appear to be chemically similar to the synthetic steroidal hormone gestrinone reported to have androgenic, anti-oestrogenic, and antiprogestogenic properties.

Until recently drug testing did not identify this steroid and thus it was not reported as a positive finding. In the current IOC Anti-doping code and the 2004 WADA code Anabolic agents are prohibited. According to the codes, all analogues of anabolic agents are prohibited whether specifically named or not in the code.