TNF and polycystic ovary syndrome: With regard to the subgroup analysis by ethnicity, significantly higher TNF-α levels were found in patients with PCOS in both Caucasian (SMD = 0.308, 95%CI = 0.005–0.612, P = 0.047, I2 = 79.8%) and Asia ethnicity (SMD = 1.103, 95%CI = 0.489–1.718, P = 0.000, I2 = 94.0%) (S1 Fig, Table 2).