Tribulus Terrestris to high libido

Tribulus is most often used for infertility, erectile dysfunction, and low libido. In the last decade, it has become popular to improve sports performance.

Tribulus has been marketed these conditions because research performed in Bulgaria and Russia indicates that tribulus increases levels of the hormones testosterone (by increasing luteinizing hormone), DHEA, and estrogen. The design of these research studies, however, has been questioned.

A more recent study found that four weeks of tribulus supplements (at 10 to 20 milligrams per kg of body weight daily) had no effect on male sex hormones testosterone, androstenedione, or luteinizing hormone compared to people who did not take tribulus.

Erectile Dysfunction
Preliminary animal studies found that tribulus heightened sexual behavior and increased intracavernous pressure. This was attributed to increases in testosterone. There haven't been any well-designed human studies to confirm these early findings.
Body Composition and Exercise Performance
Although tribulus has become popular as a sports performance aid, one small but well-designed study found it has no effect on body composition or exercise performance. Fifteen subjects were randomly assigned to tribulus (3.21 mg per kg body weight daily) or a placebo.

After eight weeks with resistance training, there were no changes in body weight, percentage fat, dietary intake, or mood in either group. What was surprising was that muscle endurance actually improved more in the placebo group. Muscle endurance (determined by the maximum number of repetitions at 100 to 200% of body weight) increased for the bench and leg presses in the placebo group. The tribulus group experienced an increase in leg press strength only.

Dosage

Tribulus terrestris is often taken at a dose between 85 to 250 mg three times daily, with meals.

Safety

Pregnant or nursing women should not use tribulus.

An increase in breast size (called gynaecomastia) in a young male weight trainer was reported after he took a herbal tablet containing tribulus.

People with hormone-dependent conditions, such as breast or prostate cancer, should not use tribulus.

Tribulus terrestris has a toxic effect in sheep. It has been found to cause a chronic, progressive, irreversible disorder in the dopamine circuits of the nigrostriatal complex in the brain, resulting in impaired muscle function and weakness in the hindquarters, eventually leading to death.
Bourke CA. "A novel nigrostriatal dopaminergic disorder in sheep affected by Tribulus terrestris staggers". Research in Veterinary Science. 43.3 (1987):347-50.

Gauthaman K et al. "Sexual effects of puncturevine (Tribulus terrestris) extract (protodioscin): an evaluation using a rat model". Journal of Alternative and Complementary Medicine. 9.2 (2003):237-65.