Obesity has become a public health problem of global concern, which can lead to systemic diseases such as hypertension, coronary heart disease, dyslipidemia, diabetes, respiratory sleep apnea syndrome, abnormal bone metabolism and malignant tumors. Numerous studies have shown that there is a causal relationship between obesity and abnormal gonadal function, which can lead to male infertility and female infertility. Therefore, this paper focuses on the relationship between obesity and gonadal function. First, obesity causes hypogonadism Obesity and male infertility and female infertility mechanism 1, obesity causes male infertility (1) reproductive endocrine abnormalities: white adipose tissue contains high levels of aromatase P450, P450 is an important rate-limiting enzyme for the conversion of androgens into estrogen, resulting in overexpression of estrogen, thus negatively inhibiting the secretion of pituitary gonadotropin and reducing testosterone secretion by the testes . At the same time, the hypothalamic-pituitary-gonadal axis (HPG) can be abnormally affected by leptin, inflammatory factors, oxidative stress factors and other physical factors such as increased scrotal temperature and sleep apnea. HPG) function abnormally, affecting testosterone secretion and leading to reproductive endocrine abnormalities. (2) Erectile dysfunction: It is found that abdominal obesity is an important factor affecting male erectile function, and about 96.5% of abdominal obese patients have erectile dysfunction in combination. (3) abnormal semen parameters: research found that the obese sperm concentration decreased; with the increase in weight, the number of sperm activity decreased significantly, the movement ability decreased. 2, obesity to female infertility obesity and menstrual disorders, reproductive system tumors, polycystic ovary syndrome and miscarriage, infertility and other close relationship. It can affect a series of hormonal changes in women’s bodies, such as hyperinsulinemia, insulin resistance, hyperandrogenemia, abnormal gonadotropin secretion, increased aromatase activity, insulin-like growth factor binding proteins (insulin-likegrowth factor binding proteins, IGFBPs) reduction, sex hormone binding globulin ( sex hormone binding globulin (SHBG), and increased Leptin, leading to abnormal reproductive function. In addition, more and more evidence points out that even for young women with regular menstruation, the time spent on artificial assisted reproduction by obese women is longer than that of women with normal BMI, and it is pointed out that when BMI>29kg/m2, the pregnancy rate is 4% lower than that of women with BMI in the range of 21-29kg/m2 for every 1kg/m2 increase in BMI. Second, hypogonadism causes obesity 1, male hypogonadism causes obesity Hypogonadism is divided into high gonadotropin hypogonadism and low gonadotropin hypogonadism, both types of disease lead to testosterone deficiency. Testosterone has a role in promoting the development of male secondary sex characteristics and reducing visceral fat. And animal experiments and clinical trials have found that testosterone plays an important role in male energy metabolism and obesity. 2, female hypogonadism causes obesity Animal experiments illustrate from both positive and negative aspects that estrogen and obesity are negatively correlated: estrogen deficiency is related to weight gain, and estrogen replacement therapy is also related to weight loss. About 50% of patients with PCOS are overweight or obese, and abdominal obesity is predominant. Since androgenosis, insulin resistance and hyperinsulinemia are important metabolic features in patients with PCOS. Therefore, obesity in PCOS patients is likely to be related to the combined effect of the internal environment such as long-term androgen increase and hyperinsulinemia. Obesity and gonadal function interact in a bidirectional relationship. Obesity and testosterone deficiency cycle mechanism diagram When patients are obese their body insulin resistance increases and sex hormone binding protein decreases leading to a decrease in testosterone secretion, while obesity in turn increases estradiol, leptin and other obesity-related factors secretion, and cortisol secretion, leading to insufficient gonadotropin secretion, which further leads to a decrease in testosterone secretion. On the other hand, the accumulation of low testosterone adipose tissue, reduced muscle production, and severe insulin resistance exacerbate further weight gain. Therefore, it is important to actively prevent and control obesity.