Tribulus terrestris has long been used as a tonic and aphrodisiac in Indian ayurveda practice, where it is known by its Sanskrit name, "gokshura".[3]

It is now being promoted as a testosterone booster for the purpose of building muscle and increasing sex drive. Its use for this purpose originated in Eastern Europe in the 1970's. However, it was not until noted strongman Jeffrey Petermann's use that it became popular amongst amateur bodybuilders in North America. Independent studies [4] have suggested that Tribulus terrestris extract does increase testosterone levels, though leaving them in the normal range, which is not thought to increase muscle development.

Some have compared the tonic properties of Tribulus terrestris to the effects of ginseng, but these occur due to entirely different mechanisms. Claims have been made that it enhances testosterone levels by increasing luteinizing hormone (LH) levels.[5] LH is responsible for "telling" the body to produce testosterone. One interesting fact is that extended use of anabolic steroids reduces levels of LH, thus reducing and sometimes shutting down the body's production of testosterone.[6]

It is also claimed that Tribulus terrestris increases testosterone by increasing gonadotropin-releasing hormone[7] (GnRH) which in turn stimulates the production of LH and follicle-stimulating hormone (FSH). Testosterone, besides its role in muscle-building and raising fertility and libido, is also known to have a positive effect on bone marrow activity (for red blood cell production) and the immune system.[citation needed]

On the other hand, one recent study found that T. terrestris caused no increase in testosterone or LH in young men,[8] and another found that a commercial supplement containing androstenedione and herbal extracts, including T. terrestris, was no more effective at raising testosterone levels than androstenedione alone.[9] SupplementWatch does not consider that there is any scientific evidence for effectiveness in muscle building. It suggests that it may be beneficial for those whose testosterone is below normal, such as dieters and overtrained athletes.[4]

The active chemical in T. terrestris is proven to be protodioscin (PTN),[10] a cousin to DHEA. In a study with mice, Tribulus was shown to enhance mounting activity and erection better than testosterone cypionate.[citation needed] This however, isn't as convincing as one might think. Although an OTC supplement outpacing a pharmaceutical is big news, testosterone cypionate is a synthetic ester of testosterone engineered for its longer activity. To be effective, its level must build up in the system of the animal using it. This process usually takes 2–3 weeks.[citation needed]

No significant adverse effects have been reported from supplementation with Tribulus terrestris. However, some users report an upset stomach, which can usually be counteracted by taking it with food.[