Precocious puberty refers to the appearance of secondary sexual characteristics in boys before the age of 9 and in girls before the age of 8. 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 pseudo-precocious 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 (GnRH) 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 caused by the elevation of sex steroid hormones to the level of puberty, so only the early appearance of secondary sexual characteristics, but not the complete sexual development process. 1. Organic lesions of central nervous system, such as hypothalamus, pituitary tumor or other central nervous system lesions. 2.Precocious sexual development from peripheral sexual precocious transformation. 3.If no organic lesion is found, it is called idiopathic central precocious puberty. 4.Incomplete central precocious puberty, a special type of CPP, refers to the early appearance of the affected child with secondary sexual characteristics, whose control mechanism also lies in the activation of the hypothalamic-pituitary-gonadal axis, but its sexual characteristics development is self-limiting; the most common type is simple premature breast development, if it occurs in girls within 2 years of age, it may be due to the hypothalamic-gonadal axis being in a physiologically active state, also known as “micropuberty”. Girls have more ICPP, accounting for more than 80%-90% of CPP; while boys have the opposite, with more than 80% being organic. III. Clinical manifestations and diagnostic basis 1. The secondary sexual characteristics appear early (at an age that meets the definition) and progress according to normal developmental procedures. Girls: breast development, sudden increase in height growth rate, pubic hair development, usually presented at menarche 2 years after the beginning of breast development. Boys: testicular and penile enlargement, sudden increase in height growth rate, pubic hair development, generally 2 years after the testicular enlargement begins to present the change of voice and spermatorrhea. 2, there is a basis for gonadal development, girls are judged by ultrasound images, boys have testicular volume ≥ 4 ml. 3, the development process presents a sudden increase in height growth. 4.Gonadotropins are elevated to puberty level. 5. There may be advancement of bone age, but there is no diagnostic specificity. The most common type of incomplete central precocious puberty is simple premature breast development, which is characterized by early breast development without other secondary sexual characteristics, no coloration of the areola, and a non-progressive, self-limiting course, with the breast fading spontaneously after several months.