MSTN is involved in the regulation of oocyte maturation, and the addition of exogenous MSTN to the culture medium promotes the maturation of porcine oocytes, but as MSTN is expressed in several tissues, treatment with exogenous MSTN may lead to inhibition of oocyte expansion in the ovary, affecting the secretion of steroid hormones such as E2 and progesterone, and may promote the development of OHSS, leading to metabolic disorders in PCOS patients. The gene discussed is MSTN; the disease is polycystic ovary syndrome.