Estrogens (including estradiol) (E2) and estrogen receptors (ERs), including the ERα and ERβ isoforms, are suspected of influencing AIS severity and delayed puberty which has been directly associated with a higher prevalence of AIS in girls than in boys with an incidence ratio of 7.1:1 (Konieczny et al., 2013). This evidence concerns the gene ESR2 and androgen insensitivity syndrome.