THG — tetrahydrogestrinone

Tetrahydrogestrinone (THG) is an oral anabolic steroid derived from nandrolone. This agent is a designer steroid, meaning that it was never commercialized, but developed specifically for use by athletes due to the fact that it was once unknown (and therefore unidentifiable) to drug screening. THG is most similar in structure to the European prescription anti-gonadotropic agent gestrinone. Gestrinone is not an active anabolic steroid itself, but does have a close structural relationship to trenbolone. Adding four hydrogen atoms (tetra-hydro) to gestrinone breaks down its 17-alpha ethynyl group (a trait that greatly interferes with binding to the androgen receptor) to an ethyl, creating a steroid capable of strong anabolic and androgenic action. THG is simply 17-alpha-ethylated, gestrinone, a novel offshoot of the powerful anabolic steroid trenbolone. The resulting steroid is highly anabolic, moderately androgenic, non-estrogenic, and highly progestational.

Brand name THG, Tetrahydrogestrinone
Androgenic no data available
Anabolic no data available
Chemical Names 18a-Homo-pregna-4,9,11-trien-17b-ol-3-one
Estrogenic Activity none
Progestational Activity very high

THG History

Tetrahydrogestrinone was first described in 2004. It was brought to light in what was called "the biggest organized bust for steroid use in the history of competitive sports." These were the words of Terry Madden, Chief Executive Officer of the U.S. Anti-Doping Agency (USADA), when addressing a group of newspaper and television reporters in a press conference disclosing the international doping scandal. His accompanying press release spoke of an anonymous Olympic coach, who turned over a syringe containing the designer steroid and implicated Victor Conte of BALCO Labs in California, then credited with coaching many of the world's top athletes, as the source for the agent. The anonymous source was later identified as track coach Trevor Graham. USADA was soon amidst media frenzy, with many big names fingered for testing positive for the use of THG.

For a short period of time, THG was an ideal steroid for athletes in drug-tested sports, being both extremely effective and undetectable on a urine screen. It was also technically legal to own in the U.S., being that it was unknown to lawmakers at the time the Anabolic Steroid Control Act was written. But with the international doping scandal that would come to surround BALCO Laboratories, any value that THG held as a "designer steroid" has since disappeared. This steroid was also added to the U.S. controlled substance list in January 2005. Victor Conte would serve several months in prison for his role in the BALCO scandal, due to the fact that an unknown drug like THG may have been legal to own, but it was not legal to sell. Patrick Arnold, the chemist behind THG, pled guilty to criminal charges as well, and is scheduled to begin serving a 3-month prison term in late 2006.

Tetrahydrogestrinone was a designer steroid of opportunity, created from a readily available and unregulated intermediary chemical with a simple synthesis method. It would arise from the doping scandal fallout as the world's famous superstar of designer steroids. The existence of THG would be a constant reminder that the determination of athletes to utilize all available tools to win goes far beyond the abilities of the governing athletic bodies to police them. Until much more effective drugtesting methods are developed, which rely not on structural and metabolic knowledge of the various substances but can actually determine if a new previously unidentified steroid is being used, THG will also be a reminder that it is possible, if not highly likely, that many other designer steroids are out in the field of use at this very moment.

How is THG Supplied

Tetrahydrogestrinone is not available as a prescription drug product.

Structural Characteristics of THG

Tetrahydrogestrinone is a modified form of nandroione. it differs by: 1) the addition of an ethyl group at carbon 17-alpha to protect the hormone during oral administration, 2) the introduction of double bonds at carbons 9 and 11, which greatly increase relative steroid activity, and 3) the possession of an 18a-homo group, which gives the steroid strong progestational activity.

THG Side Effects (Estrogenic)

Tetrahydrogestrinone is not aromatized by the body, and is not believed to be measurably estrogenic. Gynecomastia remains a concern during treatment, however, due to its progestational nature (see below), especially when combined with other estrogenic drugs. At the same time water retention can become a problem, causing a notable loss of muscle definition as both subcutaneous water retention and fat levels build. To avoid such strong side effects, it may be necessary to use an anti-estrogen such as Nolvadex®.

Note that tetrahydrogestrinone is an extremely active progestin. In assays it was shown to have stronger progestational activity than nandroione, trenbolone, and even gestrinone, a synthetic progestin. THG was actually shown to be 7 times more potent than progesterone itself. The side effects associated with progesterone are similar to those of estrogen, including negative feedback inhibition of testosterone production and enhanced rate of fat storage. Progestins also augment the stimulatory effect of estrogens on mammary tissue growth. There appears to be a strong synergy between these two hormones here, such that gynecomastia might even occur with the help of progestins without excessive estrogen levels being present. The use of an anti-estrogen, which inhibits the estrogenic component of this disorder, is often sufficient to mitigate gynecomastia caused by progestational steroids.

THG Side Effects (Androgenic)

Although classified as an anabolic steroid, androgenic side effects are still common with this substance. This may include bouts of oily skin, acne, and body/facial hair growth. Anabolic/androgenic steroids may also aggravate male pattern hair loss. Women are additionally warned of the potential virilizing effects of anabolic/androgenic steroids. These may include a deepening of the voice, menstrual irregularities, changes in skin texture, facial hair growth, and clitoral enlargement. Note that THG does not appear to be subject to 5-alpha reduction, so its relative androgenicity is not affected by the concurrent use of finasteride or dutasteride.

THG Side Effects (Hepatotoxicity)

Tetrahydrogestrinone is a cl 7-alpha alkylated compound. This alteration protects the drug from deactivation by the liver, allowing a very high percentage of the drug entry into the bloodstream following oral administration. 0 7-alpha alkylated anabolic/androgenic steroids can be hepatotoxic. Prolonged or high exposure may result in liver damage. In rare instances life-threatening dysfunction may develop. It is advisable to visit a physician periodically during each cycle to monitor liver function and overall health. Intake of cl 7-alpha alkylated steroids is commonly limited to 6-8 weeks, in an effort to avoid escalating liver strain. Severe liver complications are rare given the periodic nature in which most people use oral anabolic/androgenic steroids, although cannot be excluded with this steroid, especially with high doses and/or prolonged administration periods.

THG Side Effects (Cardiovascular)

Anabolic/androgenic steroids can have deleterious effects on serum cholesterol. This includes a tendency to reduce HDL (good) cholesterol values and increase LDL (bad) cholesterol values, which may shift the HDL to LDL balance in a direction that favors greater risk of arteriosclerosis. The relative impact of an anabolic/androgenic steroid gn serum lipids is dependant on, the dose, route of administration (oral vs. injectable), type of steroid (aromatizable or non-aromatizable), and level of resistance to hepatic metabolism. Tetrahydrogestrinone has a strong effect on the hepatic management of cholesterol due to its structural resistance to liver breakdown, non-aromatizable nature, and route of administration. Anabolic/androgenic steroids may also adversely affect blood pressure and triglycerides, reduce endothelial relaxation, and support left ventricular hypertrophy, all potentially increasing the risk of cardiovascular disease and myocardial infarction.

To help reduce cardiovascular strain it is advised to maintain an active cardiovascular exercise program and minimize the intake of saturated fats, cholesterol, and simple carbohydrates at all times during active AAS administration. Supplementing with fish oils (4 grams per day) and a natural cholesterol/antioxidant formula such as Lipid Stabil or a product with comparable ingredients is also recommended.

THG Side Effects (Testosterone Suppression)

All anabolic/androgenic steroids when taken in doses sufficient to promote muscle gain are expected to suppress endogenous testosterone production. Without the intervention of testosterone-stimulating substances, testosterone levels should return to normal within 1-4 months of drug secession. Note that prolonged hypogonadotrophic hypogonadism can develop secondary to steroid abuse, necessitating medical intervention.

THG Administration (General)

Prescribing guidelines generally advise that oral steroids can be taken with or without meals. The difference in bioavailability is generally not regarded as substantial. However, a 2016 study on newborn infants did find the absorption of oxandrolone to be significantly improved when dissolved directly in fat (MCT oil). If the diet includes considerable fat content, taking this oral steroid with meals might be more advantageous.

THG Administration (Men)

Tetrahydrogestrinone was never approved for use in humans. Prescribing guidelines are unavailable. Methyltrienolone is its closest chemical relative, and known to be effective in doses lower than Img per day. THG should also require very small doses, perhaps in the range of 2-5 mg per day. We can also note that THG minus its delta-11 modification (a di-ene instead of a tri-ene) has been documented to be over 14 times more active than methyltestosterone. There is no reason to think that the' jump to THG would be anything but an improvement. Although exact figures don't exist, this designer steroid should be far more potent than any anabolic steroid commercially available, and would probably fall slightly short of methyltrienolone. For those athletes who use THG, the results should be measurable improvements in strength, muscle size, and performance.

THG Administration (Women)

Tetrahydrogestrinone was never approved for use in humans. Prescribing guidelines are unavailable. THG is generally not recommended for women for physique- or performance-enhancing purposes due to its very strong nature and tendency to produce virilizing side effects. This compound could be used with success, but only with a commercial preparation that makes measuring out the very low (microgram) amounts needed with females possible.

THG Availability

THG is unavailable as a prescription drug product. It is available as an underground steroid only.


Wlliam Llewellyn (2017) - Anabolics

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