According to Wikipedia, Tribulus terrestris, also called bullhead, burra gokharu, caltrop, cat's head, devil's eyelashes.etc,  is a flowering plant in the family Zygophyllaceae, native to warm temperate and tropical regions of the Old World in southern Europe, southern Asia, throughout Africa, and Australia. It can thrive even in desert climates and poor soil. 

 

Tribulus Terrestris Extract Powder, always extracted from the fruit of the Tribulus Terrestris, has long been a popular medicinal herb in Bulgaria, Eastern Europe, Asia and India for treatment of sexual deficiencies.

Apart from its claims for improvement of sexual functions in men, the Tribulus Terrestris Extract has long been considered as an energizer and vitalizer in the indigenous system of medicine.

Protodioscin is a steroidal saponin compound found in a number of plant species, mostly in the Tribulus families. It is best known as the putative active component of the herbal aphrodisiac plant Tribulus terrestris.

Extracts from T. terrestris for protodioscin content have been demonstrated to produce proerectile effects in isolated tissues and aphrodisiac action in several animal species. The mechanism for these effects has not been clearly established, and while protodioscin has been demonstrated to trigger release of nitric oxide in corpus cavernosum tissue, and also to produce statistically significant increases in the levels of the hormones testosterone, dihydrotestosterone and dehydroepiandrosterone in animal studies, but studies in humans have failed to show efficacy and its use remains controversial.

As I said above, Protodioscin, extracted from the fruit of the Tribulus Terrestris has mechanism that might increase some hormones in animals. However, it doesn't appear to increase male hormones (testosterone) in humans.

Tribulus terrestris is a popular herbal supplement that is used to increase testosterone levels, sex drive, and DHEA. Below are some key health benefits of Tribulus Terrestris.

The compound is rich in saponins, the active ingredient claimed to increase the body’s natural testosterone levels and helps to build muscle. Many manufacturers cite a study done by Milanov, et al., showing that T. terrestris elevated luteinizing hormone (LH) and increased free testosterone levels in healthy males, but Edmund R. Burke, a physiological researcher, said, “there is no conclusive evidence that tribulus enhances muscle growth or strength.” Bodybuilders who have used anabolic steroids believe that this supplement can help with postcycle therapy and restore natural testosterone levels.

There are several claims about what tribulus terrestris supplements can do for the body. The two most common reasons people begin taking the supplements is to increase sexual desire and to increase muscle mass. Athletes especially are attracted to the muscle-building properties promoted by tribulus terrestris claims. People have also taken tribulus terrestris to treat serious illnesses such as cancer, kidney problems and blood pressure problems.

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

Side effects of Tribulus terrestris are extremely rare, and very few have been reported.

The most commonly reported side effect of taking Tribulus terrestris extract is mild stomach pain, which may or may not be accompanied by feelings of nausea. In most cases the problem can be averted by taking Tribulus extract with – or shortly after – food. If you are prone to upset stomachs then taking the supplement with a food such as live yoghurt will almost certainly prevent any discomfort.