a) There’s evidence that nettle root extract can relieve symptoms of bening prostate hyperplasia (study).
b) There’s also evidence that in rodents, nettle root could increase testosterone levels in rodents (study). And several in-vitro studies shows that the lingans in nettle root can block SHBG from binding into hormones, and thus increase free-testosterone and free-DHT levels. Nettle root was in fact so powerful in a test-tube that it even displaces hormones from SHBG, making them bio-available for the receptors (study, study, study, study)
c) However, the above studies on SHBG were done in-vitro, and in the only human study where the subjects took nettle root extract orally, there was no increase in testosterone. What’s worse is that there’s some evidence of the herb acting as 5-a enzyme inhibitor, meaning that not only did it do nothing to testosterone, there’s a possibility that it could also decrease DHT levels.
from article titled " http://www.anabolicmen.com/herbal-testosterone-booster-guide/"
Doesn't look like its worth much use, there are better options out there.