CYP19A1 and polycystic ovary syndrome: These results are also relevant for our understanding of the steroidal consequences in polycystic ovarian syndrome (PCOS), where antral follicles appear to be arrested in an early differentiation state, with limited aromatase expression and high levels of secreted steroid precursors (Franks et al., 2000) as well as INSL3 (Anand-Ivell et al., 2013).