Does Tribulus terrestris L. affect hormonal responses following high-intensity resistance exercise?

Abstract Study aim: To investigate the effect of a 2-week supplementation with Tribulus terrestris L. (TT) on the responses of testosterone, cortisol, and thyroid hormones including triiodothyronine (T3) and thyroxine (T4) following an intensive session of resistance exercise (RE). Materials and methods: Twenty-two healthy non-athlete men (23.8 ± 3.1 years) participated in this study were divided into two groups and were randomly assigned to receive either TT supplementation (n = 11) or a placebo (n = 11). They consumed two 250-mg capsules with TT or placebo (maltodextrin) per day and performed six REs with the intensity 80-90% of 1RM on the fifteen day of the experiment. Venous blood samples were drawn before supplementation, and before and after the RE session. Results: The mean values of post-exercise testosterone and cortisol in both groups were significantly higher than pre-exercise and baseline (p < 0.01); however, there were no significant differences between the groups (p > 0.05). Likewise, despite a trend toward different levels of the responses of thyroid hormones with TT supplementation, there were no significant differences either in different time points or the groups (p > 0.05). Conclusions: Short-term supplementation with TT appears to be ineffective in changing the hormonal responses measured in this study following a session of high-intensity RE.