AR and partial androgen insensitivity syndrome: In PAIS however, mutations of the AR gene are detected in <25% of patients whilst a complementary causative role has been ascribed to genetic variants of the protein and cofactors that concur to the AR signaling pathway, such as the deficiency 17β-hydroxysteroid dehydrogenase (17β-HSD), a key enzyme in steroidogenesis (133, 134).