Some body builders use T. terrestris as post cycle therapy or "PCT".[citation needed] After they have completed an anabolic-steroid cycle, they use it under the assumption that it will restore the body's natural testosterone levels.
The extract is claimed to increase the body's natural testosterone levels and thereby improve male sexual performance and help build muscle. Its purported muscle-building potential was popularized by American IFBB bodybuilding champion Jeffrey Petermann in the early 1970s. However, T. terrestris has failed to increase testosterone levels in controlled studies.[10][11][12]It has also failed to demonstrate strength-enhancing properties[13] - a finding indicating that the anabolic steroid effects of Tribulus terrestris may be untrue. Some users report an upset stomach, which can usually be counteracted by taking it with food.[citation needed]
Traditional medicine
In traditional Chinese medicine Tribulus terrestris is known under the name bai ji li (白蒺藜). According to Bensky and Clavey, 2004 (Materia medica 3rd edition, pp. 975–976) Tribulus terrestris is ci ji li (刺蒺藜). "Confusion with Astragali complanati Semen (sha yuan zi) originally known as white ji li (白蒺藜 bai ji li), led some writers to attribute tonifying properties to this herb..."
T. terrestris has long been a constituent in tonics in Indian Ayurveda practice, where it is known by its Sanskrit name, "gokshura/ sarrata"[14] It is also used in Unani, another medical system of India.
Research in animals
T. terrestris has been shown to enhance sexual behavior in an animal model.[15] It appears to do so by stimulating androgen receptors in the brain.T. terrestris is now being promoted as a booster for the purpose of increasing sex drive. Its use for this purpose originated from a Bulgarian study conducted in the 1970s, which found effects on free testosterone and luteinizing hormone in men belonging to infertile couples.[citation needed] A research review conducted in 2000 stated that the lack of data outside of this study prevents generalizing to healthy individuals [16]
Animal studies in rats, rabbits and primates have demonstrated that administration of Tribulus terrestris extract can produce statistically significant increases in levels of testosterone, dihydrotestosterone and dehydroepiandrosterone,[17] and produces effects suggestive of aphrodisiac activity.[15] On the other hand, one recent study found that T. terrestris caused no increase in testosterone or LH in young men,[18] 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.[19]
The active chemical in T. terrestris is likely to be protodioscin (PTN).[20] In a study with mice, T. terrestris was shown to enhance mounting activity and erection better than testosterone cypionate;[citation needed] however, testosterone cypionate is a synthetic ester of testosterone engineered for its longer activity, rather than an immediate effect. Testosterone cypionate has a half-life of 8 days and is administered every 2–4 weeks in humans for testosterone replacement.[21] The proerectile aphrodisiac properties were concluded to likely be due to the release of nitric oxide from the nerve endings innervating the corpus cavernosum penis.[citation needed] Also, T. terrestris was shown to have strong inhibitory activity on COX-2.[22]