Precocious puberty is defined as the onset of secondary sexual characteristics in boys before the age of 9 years and in girls before the age of 8 years. According to the pathogenesis and clinical manifestations, there are central (gonadotropin-releasing hormone-dependent) precocious puberty and peripheral (non-gonadotropin-releasing hormone-dependent) precocious puberty, which used to be called true precocious puberty and pseudoprecocious puberty, respectively. Central precocious puberty has the same programmed process of hypothalamic-pituitary-gonadal axis (HPGA) initiation and maturation as normal pubertal development until the reproductive system matures; that is, the hypothalamus secretes and releases gonadotropin-releasing hormone early, which activates the pituitary gland to secrete gonadotropin to develop the gonads and secrete sex hormones, resulting in the development of internal and external genitalia and the appearance of secondary sexual characteristics. Peripheral precocious puberty is due to the elevation of sex steroid hormones in the body to the level of puberty caused by various reasons, so only the early appearance of secondary sexual characteristics, but does not have a complete sexual developmental process.