It was found that ERα KO adult mice display polycystic ovary, increased expression of LH receptors in ovarian follicular cells and granulosa cells, and increased concentration of serum LH, androgen, and estradiol levels (Couse et al., 2003), which indicates abnormal expression of ERα plays an important role in PCOS ovarian disease. The gene discussed is ESR1; the disease is polycystic ovary syndrome.