4-Androstenediol, also known as androst-4-ene-3β,17β-diol, is an androstenediol that is converted to testosterone. The conversion rate is about 15.76%, almost triple that of 4-androstenedione, due to utilization of a different enzymatic pathway. There is also some conversion into estrogen, since testosterone is the metabolic precursor of the estrogens. 4-Androstenediol is very weakly estrogenic. It has approximately 0.5% and 0.6% of the affinity of estradiol at the ERα and ERβ, respectively.