I. About children’s tiny puberty At birth, the hypothalamic-pituitary-gonadal (testicular or ovarian) axis, as one of the important endocrine regulatory systems in the body, is not yet as stable as that of adults, but has basically completed its establishment. Before birth, this system is temporarily put on hold in the mother’s body due to the large amount of estrogen produced by the placenta. After birth, as the umbilical cord is cut, the fetus loses its connection to the mother and the fetal endocrine system must begin to learn to carry the burden alone. Soon after leaving the mother’s body, future men in particular begin to commission the operational functions of their reproductive endocrine system within minutes, secreting androgen levels up to the low end of normal adult male levels. At this time, the testicles are mildly enlarged, there is penile erection, and even a transient manifestation of a little facial acne, which can last until about half a year of age; compared to baby boys, baby girls respond a little slower, but also begin to debug their reproductive endocrine system within a few hours. At this time, this system is not yet very stable and can produce estrogen intermittently. During this time, estradiol levels can fluctuate between 0 and 50 pg/ml (equivalent to the lower limit of estrogen levels in normal adult women). Some female infants who are sensitive to estrogen may show more pronounced breast development. Due to fluctuations in estrogen levels, a very few infants may even experience a little bleeding similar to menstruation in adolescent girls. These manifestations are usually short-lived and not very pronounced, but can occur before the age of 2 years. This manifestation in infancy is extremely similar to the process of true puberty. Therefore, the medical term for it is “minipuberty”. Minipuberty can be thought of as a mini-rehearsal for the real “big” puberty a few years later. The actual meaning of minipuberty is not well understood, and its manifestations vary from person to person. It is often overlooked, but it is indeed a physiological phenomenon that exists early in our lives. Precocious puberty in children is a relative concept of time, which refers to the appearance of secondary sexual characteristics at an earlier age than normal people of the same generation, race and gender. The age of puberty of normal people varies with the times and there is a tendency to advance constantly. For present purposes, the appearance of visible secondary sexual characteristics and/or the onset of menstruation before the age of 8 years for girls and the appearance of secondary sexual characteristics and/or a testicular volume of ≥4 ml on one side before the age of 9 years for boys are considered precocious. This suggests that the necessary medical tests should be performed to exclude the presence of health-impairing diseases in the body. There are various ways to classify precocious puberty in children. In order to guide the etiological diagnosis and treatment, it is clinically classified into: central (true) precocious puberty and peripheral (pseudo) precocious puberty mainly according to its different pathogenesis. Central precocious puberty is exactly the same as the real puberty development process, it has the participation of hypothalamus-pituitary-gonadal (testes or ovaries) axis, which can produce germ cells and can have the ability to have children; peripheral precocious puberty only has the development of secondary sexual characteristics caused by the action of sex hormones, without the participation of hypothalamus-pituitary-gonadal axis. In peripheral precocious puberty, there is only the development of secondary sexual characteristics caused by the action of sex hormones, without the participation of hypothalamus-pituitary axis system, which cannot produce sperm or eggs, and therefore does not have the ability to have children. The causes of true precocious puberty are complex and can be caused by organic diseases such as intracranial infections, trauma or tumors that trigger the “switch” of puberty development, or by so-called idiopathic central precocious puberty for which no cause can be found; the sex hormones that cause the development of secondary sexual characteristics in peripheral precocious puberty can come from in vivo or in vitro. In vivo, it can come from various tumors that secrete sex hormones, and in vitro, it can come from food or drugs. According to the degree of development of secondary sexual characteristics, there are: complete (true) precocious puberty, partial (pseudo) precocious puberty, simple breast development, simple precocious pubic hair, etc. According to whether the hypothalamic-pituitary-gonadal axis is actually activated or not, there are two categories: gonadotropin-dependent (true) and gonadotropin-non-dependent (pseudoprecocious) precocious puberty. Treatment with a long-acting gonadotropin-releasing hormone analogue (GnRH-a) is effective in the former but not in the latter. In short, the various classification methods may overlap with each other. Premature breast development alone and infants can have premature breast development alone means that girls only have early breast development without the appearance of other sexual characteristics (e.g. pubic hair, axillary hair), and there is no advancement of bone age or growth acceleration. Most of them occur in infants and children aged 6 months to 2 years, and are often caused by micro-pubescence. Premature breast development alone can also occur in childhood (2 to 8 years of age) and the mechanism of occurrence is not identical to that in infancy. In addition to the instability of the hypothalamic-pituitary-gonadal axis, the occurrence of premature simple breast development in childhood may be related to the following factors: a long-term high-protein diet, the influence of estrogen-like pollutants in the environment, the intake of foods containing sex hormones, and frequent exposure to sex-related media. What is clear is that the hypothalamic-pituitary-gonadal axis is not yet fully activated in cases of premature development of simple breasts. Peripheral precocious puberty, also known as pseudoprecocious puberty or gonadotropin non-dependent precocious puberty, refers to children with only early development of secondary sexual characteristics, but no maturation of gonadal function (ovulation or spermatogenesis), no real activation of hypothalamic-pituitary-gonadal axis, but is related to elevated levels of endogenous or exogenous sex hormones unrelated to hypothalamic GnRH. The symptoms of precocious puberty are often one of the clinical manifestations of an underlying disease and are not an independent disease. Therefore, treatment of patients with pseudoprecocious puberty should cut off the source of sex hormone production, and treatment with the drug used to treat central precocious puberty, the long-acting gonadotropin-releasing hormone analogue (GnRH-a), is ineffective. There are many causes of pseudoprecocious puberty. In both boys and girls, tumors of the gonads that secrete sex hormones, adrenocortical hyperplasia or tumors, and ingestion or repeated high exposure to exogenous sex hormones are the most common causes of pseudoprecocious puberty.