Tribulus Terrestris has been shown to boost the bodies natural production of testosterone. When this increase is combined with a controlled well thought out diet and weight training regime it can produce significantly improved and visible gains in muscle mass and strength. The active ingredient (protodioscin) increases secretion of luteinizing hormone (LH) from the pituitary gland. LH directly stimulates the testis production of testosterone naturally. Historical records reveal that tribulus has been used for centuries to boost libido. Until a few years ago, tribulus was a well guarded secret of the eastern european athletes for many years. Tribulus is harvested in several counties however, Bulgarian tribulus has been shown to contain higher protodioscin levels than some of these other sources. Most of the clinical studies into the benefits of tribulus terrestris have been carried out on tribulus grown in Bulgaria.