SDR16C5 and polycystic ovary syndrome: PCOS theca cells express a set of vitamin A enzymes that are sufficient for atRA biosynthesis, including retinol dehydrogenase 2 (Rdh2), retinol dehydrogenase (RoDH4,2), cellular retinoic acid binding protein II (Crabp II), and prostate short chain dehydrogenase/reductase (Psdr2) [138], and Aldh1a3 [128].