http://fitpharmcn.com/products/tribulus-terrestris-p-e/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 suggested 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.