Tribulus Terrestris is a taprooted herbaceous plant that grows as a summer annual in temperate climates. Both the root and fruit of the plant have been used medicinally in Traditional Chinese Medicine and Indian Ayurveda medicine. Its various parts contain a variety of chemical constituents that are medicinally important, such as flavonoids, flavonol glycosides, steroidal saponins, and alkaloids. It has diuretic, aphrodisiac, immunomodulatory, antidiabetic, absorption enhancing, cardiotonic, central nervous system, hepatoprotective, anti-inflammatory, analgesic, antispasmodic, anticancer, antibacterial, anthelmintic, larvicidal, and anti-cariogenic activities etc. (1) 

Tribulus Terrestris, in particular, is known to play an important role in increasing the secretion and muscle of growth hormones. A study of a group of middle-aged men has shown Tribulus Terrestris supplementation caused an increase in resting concentrations of growth hormone (GH) and insulin growth factor-1 (IGF-1) in the experimental group compared to the placebo group. (2) In another study, Tribulus Terrestris promoted large gains in strength and lean muscle mass. In the study, eleven Australian elite male rugby league players were assigned to determine the effect of Tribulus Terrestris on strength, fat-free mass during 5 weeks of preseason training. The study has shown a significant increase in strength and fat-free mass in Australian rugby league players after the 5 weeks of training. (3) In addition, according to a study of rats with Tribulus Terrestris treatment saponins significantly improved the performance of the overtraining rats, reflected by the extension of time to exhaustion, with a concomitant increase in body mass, relative mass, and protein levels of the gastrocnemius. (4) The Tribulus Terrestris extract-treated group increased the testosterone and insulin growth factor-1 (IGF-1) plasma levels, and androgen receptor, IGF-1 receptor (IGF‑1R) and myosin heavy chain protein levels in the gastrocnemius of rats. (5) 

Tribulus Terrestris may also help blood sugar control and improve cholesterol in people with diabetes. One study examined the effects of taking 1,000 mg of Tribulus Terrestris per day in 98 women with type 2 diabetes. After three months, women taking the supplement experienced lower blood sugar and cholesterol levels, compared to those who took a placebo. (6) Animal studies have also shown that Tribulus Terrestris may reduce blood sugar levels, help protect against blood vessel damage and help prevent increases in blood cholesterol. (7, 8)

In addition, Tribulus Terrestris has several other effects on the body. Tribulus Terrestris extract can be used as an anticancer drug for hepatocellular carcinoma patients. It blocks proliferation and induces apoptosis in human liver cancer cells through the inhibition of NF-κB signaling. (9) Also, Tribulus Terrestris inhibits the expression of mediators related to inflammation and expression of inflammatory cytokines, which has a beneficial effect on various inflammatory diseases. (10) It has been found to alleviate symptoms of menopause, such as hot flushes, depression and emotional instability. It may also act as a diuretic and increase urine production. (11) 

References: 

1. Chhatre S, Nesari T, Somani G, Kanchan D, Sathaye S. Phytopharmacological overview of Tribulus terrestris. Pharmacogn Rev. 2014 Jan;8 (15): 45-51. doi: 10.4103/0973-7847.125530. 

2. Michał Wilk , Małgorzata Michalczyk , Jakub Chycki , Miłosz Czuba , Robert Roczniok , Artur Gołaś , Adam Zając , Adam Maszczyk Endocrine Responses to Physical Training and Tribulus Terrestris Supplementation In Middle-Age Men Central European Journal of Sport Sciences and Medicine. 2016 13 (1): 65-71. 

3. Rogerson S, Riches CJ, Jennings C, Weatherby RP, Meir RA, Marshall-Gradisnik SM. The effect of five weeks of Tribulus terrestris supplementation on muscle strength and body composition during preseason training in elite rugby league players. J Strength Cond Res. 2007 May; 21(2): 348-53. 

4. Yin L, Wang Q, Wang X, Song LN. Effects of Tribulus terrestris saponins on exercise performance in overtraining rats and the underlying mechanisms. Can J Physiol Pharmacol. 2016 Nov; 94 (11): 1193-1201. 

5. Wu Y, Yang H, Wang X. The function of androgen/androgen receptor and insulin growth factor 1/insulin growth factor 1 receptor on the effects of Tribulus terrestris extracts in rats undergoing high intensity exercise. Mol Med Rep. 2017 Sep; 16 (3): 2931-2938. 

6. Samani NB, Jokar A, Soveid M, Heydari M, Mosavat SH. Efficacy of the Hydroalcoholic Extract of Tribulus terrestris on the Serum Glucose and Lipid Profile of Women With Diabetes Mellitus: A Double-Blind Randomized Placebo-Controlled Clinical Trial. J Evid Based Complementary Altern Med. 2016 Oct; 21 (4): NP91-7. doi: 10.1177/2156587216650775. Epub 2016 Jun 2. 

7. Mingjuan Li, Weijing Qu, Yifei Wang, Hong Wan, Cuiping Tian. Hypoglycemic effect of saponin from Tribulus terrestris Journal of Chinese Medicinal Materials. 2002 Jun; 25 (6): 420-422 

8. Tuncer MA, Yaymaci B, Sati L, Cayli S, Acar G, Altug T, Demir R. Influence of Tribulus terrestris extract on lipid profile and endothelial structure in developing atherosclerotic lesions in the aorta of rabbits on a high-cholesterol diet. Acta Histochem. 2009; 111 (6): 488-500. 

9. Kim HJ, Kim JC, Min JS, Kim MJ, Kim JA, Kor MH, Yoo HS, Ahn JK. Aqueous extract of Tribulus terrestris Linn induces cell growth arrest and apoptosis by down-regulating NF-κB signaling in liver cancer cells. J Ethnopharmacol. 2011 Jun 14; 136 (1): 197-203. 

10. Joa Sub Oh, Seung Ho Baik, Eun-Kyung Ahn, Wonsik Jeong and Seong Su Hong. Anti-inflammatory activity of Tribulus terrestris in RAW 264.7 Cells (54.2) J Immunol 2012 May; 188 (Supplement 1) 54.2; 

11. Al-Ali M, Wahbi S, Twaij H, Al-Badr A. Tribulus terrestris: preliminary study of its diuretic and contractile effects and comparison with Zea mays. J Ethnopharmacol. 2003 Apr; 85 (2-3): 257-60.