I don’t know how reliable this site is but, i’ve read a few claims that protodioscin, which is found in tribulus increase 5ar2
libilov.com/en/clinical_stud … d_1996.htm
Protodioscin acts by stimulating the enzyme 5-alpha-reductase, which plays a role in the conversion of testosterone into dihydrotestosterone (Viktorof et al. 1994). In addition, protodioscin also stimulates the hypothalamus secretion of luteinizing hormone (LH), but not of follicle stimulating hormone (FSH). Protodioscin is shown to increase the density of the Leydig, but not that of the Sertoli cells, and to improve the level of spermatogonia and to increase the production of spermatocytes and spermatids without changing the diameter of the seminiferous tubules. Physically, protodioscin treatment results in increased male fertility and sexual functions.
It might be worth investigating their source.
Viktorof I., Bozadjieva E., Protich M., et al. Pharmacological, pharmacokinetic, toxicological and clinical studies on protodioscin. IIMS Therapeutic Focus Vol 2 (1994).