For many years, DHT was considered to be the main hormone guiding prostate development and function. However, the idea was challenged when in 2001 Mahendroo et al. showed that mice in which both forms of 5α-reductase had been inactivated, have a normal functional prostate [50]. The question was then raised as to what is the real function of DHT in the prostate. In 1989 we hypothesized that DHT is a precursor of an oestrogen, 5α-androstane-3β,17β-diol (3β-Adiol) and that physiological levels of an oestrogen could be produced in the total absence of aromatase [51]. We later demonstrated that 3β-Adiol is abundant in the prostate and is a good natural ligand for ERβ