What happens during puberty? Adolescent growth and physical development is a period of very significant changes in a person’s life and is an important stage in the transition from childhood to adulthood. During puberty, the sexual organs mature, which brings about various changes in physical development and bone growth: the appearance of secondary sexual characteristics, weight gain, and accelerated bone growth; in general, adolescents are able to double their weight and increase their height by about 15-20% during puberty. So how does all this happen? The testes and ovaries, which are the gonads of both sexes, are the main organs that produce sex hormones. However, the function of the testes and ovaries is also regulated by the higher nerve centers – the hypothalamus and the pituitary gland – which together form the hypothalamic-pituitary-gonadal axis. Before puberty, hypothalamic gonadotropin-releasing hormone is suppressed, but once this suppression is lifted, hypothalamic gonadotropin-releasing hormone begins to increase, resulting in a pulsatile production and release of follicle stimulating hormone and luteinizing hormone from the pituitary gland. These two hormones secreted by the pituitary gland can directly promote the development of the testes and ovaries, so eventually sex hormone levels increase and the child enters puberty. During puberty, the secretion of sex hormones and the action of pituitary growth hormone cause rapid physical growth and the appearance of different secondary sexual characteristics in both sexes. Differences in the development of boys and girls After boys and girls enter puberty, their respective patterns – the age of development, the age of peak growth, the fastest growth rate, and the duration of pubertal development and growth – are again different. In terms of age, girls enter puberty at an earlier age than boys, as well as at the age of peak pubertal growth. Girls generally begin to develop breasts at the age of 9-11, which is the earliest manifestation of puberty, and at the age of 11-12, more than half of the girls will reach the peak of development, and their height will increase by 8-10cm in a year. -The first manifestation of pubertal development is the enlargement of the testicles bilaterally. After the growth peak, the general height has reached 83%-89% of the final height, after which the growth rate of both sexes slows down, before reaching the lifetime height, girls can also increase 15-20cm, boys about 20-25cm. 20cm, boys about 20-25cm or so. After the first menstruation of girls, the height growth of boys after ejaculation or change of voice is usually about 5cm, rarely more than 7cm. the whole puberty period is 2-4 years, generally boys have a relatively longer time. What is meant by precocious puberty? The classic definition of precocious puberty is the appearance of secondary sexual characteristics before the age of 8 years for girls and 9 years for boys. In different countries and regions, due to differences in ethnicity and nutritional status, the definition needs to be based on the statistics of the nation. For example, the Lawson Wilkins Pediatric Endocrine Society in the United States currently proposes to evaluate only Caucasian girls <7 years old and African-American girls <6 years old who show signs of sexual development; Hong Kong, China, limits the definition of precocious puberty in boys and girls to 8.5 years old and 7.5 years old before; and China, at present, still uses 9 years old for boys and 8 years old for girls. Is precocious puberty harmful? Precocious puberty can significantly affect the normal growth and psychosocial health of children, resulting in lifelong short height, disproportionate body proportions, and obesity; however, studies have shown that short-term and long-term psychological sequelae are uncommon in adolescent patients with precocious puberty. In contrast, early sexual development at the edge of the age limit is often referred to as so-called non-progressive or slowly progressive precocious puberty, and some are seen as normal variants. The need for intervention is determined by careful examination and follow-up by the clinician. What are the types of precocious puberty? As mentioned earlier, the initiation of puberty requires the initiation of hypothalamic-pituitary function, based on which precocious puberty is usually classified into central precocious puberty and peripheral precocious puberty. One is called idiopathic precocious puberty, which means that no definite cause can be found; the other is called organic precocious puberty, which is caused by various other diseases, including intracranial tumors, central nervous system infections, structural abnormalities, and so on. The idiopathic one is more common in girls, while the latter one is more common in boys. Therefore, doctors will examine boys with precocious puberty very carefully, and there will be more laboratory tests than girls. In fact, these may be part of precocious puberty, or they may be normal variations of youthful development. Diagnosis process of precocious puberty Generally, parents should bring their children to the pediatric endocrinology department of the hospital after they suspect premature development. The doctor will determine whether the child has precocious puberty by asking questions and conducting a physical examination. Then, he or she will test the levels of various hormones in the hypothalamic-pituitary-gonadal axis, bone age radiographs, ultrasound of the gonads, and MRI of the skull to determine the type of precocious puberty, the presence of intracranial lesions, and the speed of bone age progression. As mentioned earlier, the pituitary gonadotropin is secreted in pulses, so the test is performed by injecting drugs to cause the secretion of pituitary gonadotropin beforehand, and then drawing blood every 30, 60, or 90 minutes to determine the highest value to determine whether puberty has occurred. Treatment of precocious puberty Different treatments are given according to the cause of precocious puberty. For peripheral precocious puberty or precocious puberty with organic lesions, treatment of the primary disease is required, avoiding exposure to possible pathways of sex hormones, etc. For central precocious puberty, GnRHa-like drugs are currently available. GnRHa has been used for more than 20 years and has a high safety profile with few side effects. It does not affect future gonadal function at the end of treatment, which means that it does not affect the child's future development. In girls, menarche can occur 1.5 to 2 years after stopping treatment, and in boys, testicles reach the level of normal peers within 2 to 5 years after stopping the drug, and the vitality and number of sperm are normal.