Urtica dioica
Also known as Stinging Nettle. Urtica dioica has been used as a folk medicine for centuries. Stinging nettle extracts are also used as an alternative therapy for benign prostatic hyperplasia (BPH, or enlarged prostate).
Cell culture experiments have shown that Urtica extracts can inhibit the binding activity of SHBG (sex hormone binding globulin). SHBG binds to testosterone, and high levels limit the amount of free testosterone able to interact with the appropriate receptors.
Urtica extracts are also used in various bodybuilding/testosterone-boosting supplements, although no human studies have been done to demonstrate that a) SHBG binding is the mechanism for Urtica’s effects on BPH; or b) Urtica extracts actually increase free testosterone in humans.