Gokshura/ Tribulis has be show to increase testosterone and DHT [ dihydrotestosterone ] .

Scientists have studied gokshura’s effect on animals and determined that the herb does have aphrodisiac properties and proerectile aphrodisiac qualities ‘possibly the result of an increase in androgen and subsequent release of nitric oxide from the nerve endings innervating the corpus cavernosum’.  

http://www.ncbi.nlm.nih.gov/pubmed/12804079

Another study on the effect of gokshura on animals noted an increase in testosterone levels which may be useful for some cases of erectile dysfunction. The increase in some of the sex hormones was possibly due to the presence of protodioscin, a steroidal saponin.

 ‘Extracts from T. terrestris standardised for protodioscin content have been demonstrated to produce proerectile effects in isolated tissues and aphrodisiac action in several animal species. It is thought protodioscin achieves this primarily through causing an increase in androgen receptor immunoreacivity, meaning it increases the concentration of androgen receptors in cells, causing the organism to become more sensitive to androgens like testosterone and DHT. '

https://en.wikipedia.org/wiki/Protodioscin,  accessed 17 August 2015