Due to diseases such as trauma, infection, tumor, or congenital abnormalities of brain structure and function, the regulatory “switch” of puberty development can be accidentally triggered prematurely, resulting in the premature initiation of puberty development and precocious puberty. This type of precocious puberty is basically similar to normal puberty initiation process, except that the initiation time is much earlier and the whole puberty period is shorter than normal, so this type of precocious puberty is called true precocious puberty. Because the hypothalamus secretes gonadotropin-releasing hormone in the pathogenesis, it is also called gonadotropin-releasing hormone-dependent precocious puberty. Just like a day in daily life when one wakes up inexplicably late at night and has difficulty sleeping, but cannot tell the exact cause, a significant proportion of children with central precocious puberty, especially in females, have no clear cause and are therefore specifically called idiopathic precocious puberty. In most cases, boys with true precocious puberty have symmetrical enlargement of the testes and sperm production, while girls have menstruation and ovulation. Thus, children with true precocious puberty are already capable of having children. It is the sex hormones that create the secondary sexual characteristics “by hand”. Conversely, it can also be said that the secondary sexual characteristics are the work of the sex hormones. As soon as the amount of androgen or estrogen reaches a certain concentration in children before puberty, secondary sexual characteristics corresponding to androgen or estrogen will be produced. Pseudo-precocious puberty is also caused by the oral intake of exogenous sex hormones (e.g., girls mistakenly taking birth control pills as sugar pills) or the development of tumors in the body that have the ability to “illegally imitate and sell” sex hormones. This is called pseudoprecocious puberty because the onset of precocious puberty is not authorized by the central brain and is therefore very different from the normal puberty development process. It is also known as non-gonadotropin-releasing hormone dependent precocious puberty because its onset does not depend on the action of gonadotropin-releasing hormone secreted by the hypothalamus. For example, in male children with certain types of congenital adrenocortical hyperplasia, the clinical manifestation of male secondary sexual characteristics is very obvious due to the secretion of large amounts of androgens by the adrenal cortex, which is a typical pseudoprecocious (or peripheral) precocious puberty. In general, boys with pseudoprecocious puberty do not show symmetrical enlargement of the testes bilaterally and do not produce sperm; girls do not ovulate but may have pseudomenstruation (hormonal fluctuation or withdrawal bleeding). Unlike true precocious puberty, children with pseudoprecocious puberty are not yet capable of having children.