PCOS appears to involve increased epimerization of myo-inositol (MI) to d-chiro-inositol (DCI) in the ovary by insulin, the consequence of which is overproduction of DCI and deficiency of MI, which in turn affects the disturbance of FSH signaling and deterioration of the quality of oocytes [95]. The gene discussed is INS; the disease is polycystic ovary syndrome.