Fig. 5.

Principles of androgen activation and inactivation. All active androgens (T, DHT, 11KT and 11KDHT) share the 3-keto-Δ⁴ and 17β-hydroxyl motifs (shown in the black frame, taking example of T). Solid arrows indicate activation reactions, while dashed arrows represent inactivating reactions and preparation for excretion. 5α-reduction is necessary to achieve maximum AR activation (DHT, 11KDHT). The 11-oxygenated androgens also require the conversion of the 11β-hydroxyl to the 11-ketone in order to obtain maximal activity (11KT and 11KDHT; dotted inset).