TNF and polycystic ovary syndrome: It is well known that chronic inflammation is a typical feature of PCOS, and studies have found that PCOS patients (whether obese or not) have significantly higher levels of circulating inflammatory factors in their blood than healthy women (Nehir et al., 2016), treatment with etanercept, a TNF-α inhibitor, can significantly inhibit androgen increase and follicular dysplasia in letrozole-induced PCOS rats (Lang et al., 2019).