When all eligible studies were pooled (8 studies), a significantly increased levels of circulating follistatin were found in PCOS patients compared with the controls (random effects, WMD = 0.44 ng/ml; 95% CI = 0.30 to 0.58, P ≤0.001) (Fig 6 and Table 2); although, a significant evidence for heterogeneity was detected (I2 = 99.2%; p = ≤0.001). Here, FST is linked to polycystic ovary syndrome.