| Claim | Verdict | |-------|---------| | Increases testosterone | (in eugonadal men) | | Improves erectile function | Weak positive (comparable to low-dose PDE5 inhibitors) | | Enhances libido | Possible (small effect, inconsistent) | | Builds muscle/strength | False | | Safe for short-term use | Yes (when product is authentic) |
The concentration of protodioscin varies wildly between commercial extracts (5% to 60% saponins). Most negative or null studies use poorly characterized extracts, while positive studies often use high-PTN extracts (e.g., Tribestan®). 3. Proposed Mechanisms of Action 3.1 The LH-Testosterone Hypothesis (Largely Debunked) The original hypothesis posited that steroidal saponins, particularly protodioscin, are metabolized into DHEA, which then stimulates the hypothalamic-pituitary-gonadal (HPG) axis to release luteinizing hormone (LH). LH would then act on Leydig cells to produce testosterone. tribulus terrestris powder extract
| Compound Class | Key Examples | Proposed Role | |----------------|--------------|----------------| | Steroidal saponins | Protodioscin (PTN), Protogracillin, Dioscin, Tribestin | Main bioactive; precursor-like structure to dehydroepiandrosterone (DHEA) | | Flavonoids | Kaempferol, Quercetin, Rutin | Antioxidant, anti-inflammatory | | Alkaloids | Harmine, Harman | Mild MAO inhibition (neuroactive) | | Lignanamides | Tribulusamide A, B | Unknown; potential antioxidant | | Phytosterols | β-sitosterol, Stigmasterol | Membrane stabilization | | Claim | Verdict | |-------|---------| | Increases