Polycystic ovarian syndrome (PCOS) is a common endocrine metabolic disorder in women of reproductive age, characterized by anovulation, hyperandrogenemia and polycystic ovarian changes on ultrasound, and about 60% of PCOS is associated with obesity. The main metabolic syndromes associated with obesity include type 2 diabetes, PCOS, hypertension, sleep apnea, and hyperlipidemia. PCOS, like type 2 diabetes mellitus, has been widely recognized, but the role of PCOS has not been reported in the literature. I. Polycystic ovary syndrome and its metabolic changes Currently, the proportion of obese people is increasing worldwide. Obesity is usually accompanied by metabolic syndrome. According to the Rotterdam standard, PCOS is a complex endocrine syndrome involving women of reproductive age, manifesting as cessation of ovulation, hyperandrogenemia, and polycystic ovaries, with a female population incidence of about 8%. It is still unclear whether obesity is necessarily related to PCOS. Compared to normal weight PCOS, overweight or obese women with PCOS are more likely to have menstrual disorders, hirsutism, elevated fasting glucose, insulin resistance, sleep apnea, hormonal and lipid metabolism disorders, and reduced success in infertility treatment. The relationship between obesity and PCOS is likely to be multifactorial and interrelated. Both obesity and PCOS can independently contribute to insulin resistance, hyperandrogenemia, and cessation of ovulation. Hyperinsulinemia increases testosterone synthesis and decreases sex hormone binding globulin production, thereby increasing free androgen levels. In addition, this mechanism also results in abnormal hypothalamocortical axis function, follicular atresia in the ovary, and hyperandrogenemia [5].PCOS can also lead to elevated serum leptin levels, leptin resistance, and related abnormalities in adipokine metabolism. In the context of obesity, adipokines can lead to hyperinsulinemia, while acting directly on the ovaries and inhibiting oocyte maturation, leading to infertility. There are multiple metabolic abnormalities in PCOS. The boundaries are unclear as to whether it is a type of metabolic syndrome or a manifestation of the metabolic syndrome. Given the overlap between the manifestations of PCOS and the metabolic syndrome, some authors have suggested that PCOS can be treated as a female subtype of the metabolic syndrome, called XX syndrome, and defined it as a metabolic syndrome in premenopausal women coupled with hyperandrogenemia and cessation of ovulation [7]. More than half of PCOS is combined with hyperinsulinemia and impaired glucose tolerance. The prevalence of hypertension in PCOS is twice as high as in the general population, and hypertension can be associated with hypertension in young PCOS, and abnormalities in blood pressure regulation are observed even in adolescent patients. PCOS is associated with increased LDL cholesterol and triglycerides, decreased HDL cholesterol, thickened carotid intima, and other dyslipidemia, which increases the probability of fatal or nonfatal cardiovascular events. 40% of patients with PCOS have diabetes before the age of 50. About 40% of adolescents with PCOS have metabolic syndrome, and the prevalence is higher in adolescents with combined obesity (>60%), showing that obesity significantly aggravates the occurrence of metabolic abnormalities even in young patients. Second, the role of weight loss surgery on PCOS lifestyle change is the first-line treatment of PCOS. Weight loss can improve insulin resistance and serum leptin levels in obese patients with PCOS, while increasing sex hormone-binding globulin. The decrease in serum insulin and leptin levels leads to improved ovulatory function. A 5% weight loss leads to improvement in menstrual irregularities and hirsutism, restoration of fasting insulin and glucose levels, and reduction in the number of ovarian follicles [9]. However, for morbidly obese patients, it is difficult to obtain and maintain adequate weight loss with lifestyle changes and structured weight loss programs alone. The role of bariatric surgery in obesity with PCOS includes four aspects: (1) weight loss, improved image, and restoration of self-confidence. (2) Restoration of normal menstrual cycles, improved ovulation, and promotion of natural conception. (3) Decrease in androgens and increase in sex hormone binding globulin. Restore estrogen/androgen ratio, improve hirsutism and restore femininity. (4) Improving insulin resistance and relieving metabolic syndrome such as diabetes and hypertension. A follow-up report of 17 patients with PCOS who underwent laparoscopic gastric bypass or gastric banding showed that after surgery most patients regained normal menstruation (12/17) and spontaneous ovulation (10/12), hirsutism was improved, androgen levels were reduced, and HOMA-IR was reduced by up to 50%. In another retrospective study analyzing 24 patients with PC0S combined with metabolic syndrome who were followed up for more than 2 years after gastric bypass, all patients returned to normal menstrual cycle, more than half of the hirsutism was cured, glycosylated hemoglobin decreased from 8.2% to 5.1% within 3 months, and almost all hyperlipidemia, hypertension and diabetes were cured. In the 11 cases of laparoscopic gastric sleeve resection for PCOS previously reported by the author, 10 cases (10/11) returned to normal menstrual cycle within 3 months after surgery, among which 6 patients with sparse ovulation before surgery returned to normal ovulation, 4 patients with hyperandrogenemia before surgery returned to normal androgen levels 3 months after surgery, and 4 patients with hirsutism had Ferriman- Gallwey hirsutism score decreased to less than 5 points. Thus weight loss surgery has a positive therapeutic effect on PCOS while effectively reducing body weight. A group of data by Skubleny et al. showed that weight loss surgery significantly improved the manifestations of PCOS such as menstrual irregularities, hirsutism, and infertility. The incidence of PCOS decreased by 40%. However, the authors concluded that the pathophysiological basis of PCOS still exists. Weight loss surgery did not cure PCOS, but rather the weight loss alone reduced its impaired pathological processes and led to an improvement in the clinical manifestations of PCOS. One study found that weight loss after bariatric surgery in morbidly obese women had a similar effect on PCOS as did medication to improve insulin resistance and lower free testosterone. The improvement in PC OS after bariatric surgery is at least partially independent of weight loss, consistent with the mechanism by which bariatric surgery improves other metabolic syndromes. After bariatric surgery for PCOS performed by the author, first menstruation often resumes 3-5 days after surgery, and some patients return to normal menstruation in this regard, with a short-term decline in testosterone and return to a normal andro/estrogen ratio. The concomitant diabetes and hypertension rapidly resolve. This phenomenon obviously cannot be explained by weight loss. The mechanism of weight loss surgery for PCOS is necessarily consistent with its improvement or cure of other metabolic syndromes. The various hypotheses put forward so far do not provide a reasonable explanation for the different ways in which weight loss surgery can improve the metabolic syndrome to varying degrees. The author proposes the gastric-centered hypothesis that surgery involving the stomach can improve the metabolic syndrome due to the possible production of unknown factors in the gastric mucosa, the reduction or disappearance of gastric stimulation by food after bariatric surgery, and the decrease in the release of this unknown hormone, which leads to changes in the pathophysiological basis of the metabolic syndrome such as insulin resistance. Given that bariatric surgery is a good treatment for PCOS, it is worth considering the question whether PCOS should be an indication for bariatric surgery? In Europe and the United States, current indications for bariatric surgery include a BMI ≥ 40 kg/m2 or BMI ≥ 35 kg/m2 with metabolic syndrome, along with an assessment of the patient’s mental health status, history of bariatric treatment, and adequate understanding of the surgical procedure. Considering insulin resistance and the similarity to metabolic syndrome, PCOS should be considered a concomitant disease of obesity. Therefore for any BMI ≥ 35 with PCOS as a surgical candidate. It is worth pointing out that the widely adopted criteria for bariatric surgery in Europe and the United States are based on the 1991 edition of the NIH guidelines for bariatric surgery. In the 25 years since the publication of this guideline, great progress has been made in the technology and safety of bariatric surgery. The goal of the surgery has also evolved from the previous pure weight loss to the simultaneous treatment of metabolic syndrome. Therefore, this guideline needs to be revised. Our guidelines for bariatric surgery for type 2 diabetes suggest that BMI > 27.5 can be considered for surgical treatment. For bariatric surgery for PCOS, corresponding guidelines are still needed. As with bariatric surgery for type 2 diabetes, the prerequisite for bariatric surgery for PCOS is a degree of obesity. For PCOS without obesity, weight loss surgery is difficult to achieve satisfactory results. Third, the impact of weight loss surgery on pregnancy Obesity with PCOS after weight loss surgery menstrual irregularities improved, at the same time androgens reduced, sex hormone binding globulin increased, luteinizing hormone (LH) and follicle stimulating hormone (FSH) level increased, ovulation function improved. Studies have shown that PCOS patients have higher pregnancy rates and lower miscarriage rates after weight loss surgery. 69 of 110 infertile obese patients became pregnant after surgery, and a postoperative BMI loss >5 predicted an increased chance of pregnancy within the next 2.5 years. It has been noted that compared to the need for medication prior to weight loss surgery to increase the chances of pregnancy, this need was significantly reduced 3 years after surgery and women who were anovulatory prior to surgery did not need to resort to ovulation-promoting drugs or in vitro fertilization to become pregnant after surgery. In the last 3 years, the author had 83 cases of obese patients with PCOS who had the intention of pregnancy, 10 cases of spontaneous pregnancy after bariatric surgery, and 1 case had a successful delivery. Is pregnancy after weight loss surgery for obesity with PCOS safe? Is the safety of pregnancy better than that of those who did not undergo bariatric surgery? Numerous studies have shown that pregnancy after bariatric surgery is safe. A controlled study of 288 pregnancies with or without bariatric surgery showed that those who underwent bariatric surgery were less likely to have hypertension and diabetes during pregnancy and to have a cesarean section, and had reduced time to delivery and low birth weight. The group had eight bariatric surgery-related complications: three cases of anemia, three cases of gastrointestinal distress, and two cases of gastric band slippage. The results of another controlled study showed that bariatric surgery cured gestational diabetes but did not reduce the incidence of gestational hypertension; there was a reduced incidence of postpartum hemorrhage, endometritis, and giant fetuses, but a higher incidence of preterm births. Little is known about the long-term status of infants born after weight loss surgery. It has also been shown that children born to mothers who have undergone bariatric surgery are about 50% less likely to be obese as adults. How long after bariatric surgery is appropriate for pregnancy? It is generally accepted that pregnancy should not occur until at least 12 months after bariatric surgery, which is the time required for weight loss and recovery from metabolic abnormalities. The fastest period of weight loss is 3 to 8 months after surgery, and during this rapid weight loss, theoretical vulnerability to nutritional and vitamin deficiencies can occur. A post-gastric banding pregnancy data showed seven unplanned pregnancies within a few months or a year after surgery, five successful deliveries and two miscarriages. In a larger sample, 104 pregnancies within 1 year (mean 7 months) after bariatric surgery were compared with 385 pregnancies more than 1 year (mean 56.7 months) after surgery in terms of co-morbidities (hypertension, gestational diabetes, anemia), fetal outcome (intrauterine growth retardation, hypohydramnios, giant fetus, birth weight, Apgar score, perinatal death), or delivery complications (induction of labor or intensification of contractions, postpartum hemorrhage, preterm labor, or surgical delivery) did not differ significantly. Since most obese patients with PCOS have irregular or absent menstruation before bariatric surgery, they are not habitual users of contraception. After weight loss surgery, menstruation and ovulation resume, and most of them are unplanned pregnancies. Taking these data together, it can be concluded that the pregnancy process is safe under the close supervision of an obstetrician for more than 8 months after weight loss surgery.