Pubertal development is the fourth stage of sexual differentiation and development in boys. At this time, the gonads secrete sufficient sex hormones to further develop secondary sexual characteristics and to perfect gonadal function. The mechanism of pubertal development is unknown, but it is currently thought to be related to leptin in the body. II. Markers of puberty onset The marker of puberty onset is the appearance of a peak in gonadotropin-releasing hormone (GnRH) pulse secretion. However, the visible marker of puberty initiation is the enlargement of the testes. The age at which testicular enlargement begins ranges from 9 to 14 years, with an average of 11.5 years. The long diameter of the testis before puberty is usually <2 cm. A long diameter of more than 2.5 cm or a volume greater than 5 ml is a sign of pubertal initiation. III. Staging of pubertal development Tanner and Marshall divided the developmental process of pubic hair (PH) and male genitalia (G), the main indicators of pubertal development, into five stages The development of pubic hair can be divided into the following five periods: 1. Stage I (PH1): the period without pubic hair. 2.Phase II (PH2): A few long hairs with no dark coloring grow at the root of the penis. 3, Phase III (PH3): the hair color becomes darker, thicker and extends to the pubic symphysis. 4.Stage IV (PH4): The characteristics of the hairs are the same as those of adults, but the area covered is smaller and has not yet extended to the medial femoral side. 5.Stage V (PH5): The distribution of hairs is inverted triangle, and it has extended down to the medial femoral side. Male genital development can also be divided into the following five developmental periods: 1, stage I (G1): pre-pubertal state. 2.Stage II (G2): The testicles begin to grow, with a length and diameter greater than 2.5 cm. The scrotum also grows and becomes reddish in color. 3.Stage III (G3): The penis begins to grow, grow and thicken, and the testicles and scrotum grow further. 4.Stage IV (G4): The glans begins to develop, the penis, testicles and scrotum grow further, the scrotal skin folds and the pigment deepens. 5.Stage V (G5): The size and shape of the genitalia are like those of adults. The whole process of puberty lasts 4~5 years, but the development of genital organs and pubic hair is not synchronized, and it may be normal to have pubic hair growth before genital development or no pubic hair during G4. During puberty, the growth of height is accelerated, which is called pubertal growth. The average height growth is about 28 cm from the beginning of the growth spurt to the end of the growth spurt; the first growth spurt is the growth of the feet, then the calves and then the thighs after 4 months. About 6 months after the legs reach their maximum growth rate, the torso reaches its maximum growth rate. Before the trunk reaches its maximum growth rate, the height has already reached its highest growth rate. The driving force behind sudden growth in boys is androgens, and growth hormone (GH) also plays a role. Also need the right amount of thyroid hormone and adrenal cortical hormone. V. Conditions of pubertal development Normal pubertal development must have normal endogenous and exogenous environment and conditions. Endogenous environmental factors include hormones, local paracrine hormones and cytokines that regulate pubertal development and the normal regulatory relationship between them. The pituitary gland, gonads have normal histology and target cell responses to hormones, etc. Exogenous factors include proper physical activity and nutritional supply. Normal pubertal development can be affected if physical activity is excessive, too little, malnutrition or overnutrition. Delayed pubertal development is called delayed pubertal development when the boy’s testicles are less than 4ml bilaterally at the age of 14, or when pubic hair does not appear at the age of 15. The incidence of delayed puberty is about 5%, among which somatic delay (familial, no organic lesion) is the most common, and other causes include primary hypogonadism (testicular lesion), secondary hypogonadism (hypothalamic-pituitary lesion), androgen receptor insensitivity, etc. The focus of the management of delayed puberty is to identify somatic developmental delay from secondary hypogonadism, which is difficult and is determined in combination with olfaction, other abnormalities of the genitourinary system, familial delayed puberty and GnRH test. Opinions on the timing of management of delayed pubertal development are mixed. Regardless of the cause of delayed puberty, early treatment is better than late treatment, i.e. not earlier than 14 years old and not later than 16-18 years old! The need for treatment of somatic developmental delay depends on the child’s condition, and short-term application of testosterone (several months?) is possible to improve secondary sexual characteristics and psychological feelings. But it should also be after the age of 14 to avoid early healing of the epiphysis, which can affect height.