Puberty is a complex biological developmental process during which the reproductive system matures, and secondary sexual characteristics develop. It normally begins between the ages of 8 and 13 in girls and between the ages of 9 and 14 in boys. However, a recent trend towards earlier onset of puberty has been observed, which has raised many questions. Early or precocious puberty is defined as the appearance of pubertal signs before the age of 8 in girls and before the age of 9 in boys. The question arises as to whether early puberty is a natural trend or a serious public health issue with long-term consequences.

Biochemistry of organismal maturation

The onset of puberty is regulated by the hypothalamic-pituitary-gonadal axis (HPG axis). The hypothalamus secretes gonadotropin-releasing hormone (GnRH), which then stimulates the pituitary gland to secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These hormones are responsible for stimulating the gonads to produce sex steroids – estradiol in girls and testosterone in boys, which leads to the development of secondary sexual characteristics and reproductive maturity. More recent research has highlighted the roles of proteins MKRN3 and DLK1, inhibitors of the onset of puberty, as well as the neuropeptide kisspeptin, which stimulates the activation of the HPG axis, and its receptor, KISS1R.

Multifactorial etiology of precocious puberty

The trend towards earlier puberty has been observed mostly in industrialized countries. Improvements in nutrition and health conditions, reductions in infectious diseases, and increases in body mass are thought to contribute to earlier maturation. Genetic triggers for earlier puberty include mutations in the MKRN3 and DLK1 genes, genes involved in the regulation of GnRH neurons, which lead to earlier activation of the HPG axis. Furthermore, both obesity and increased body fat mass are associated with earlier pubertal development, particularly in girls. Adipose tissue produces leptin, a hormone that signals energy availability and can trigger the onset of puberty.

However, there is growing evidence that environmental factors may also play a significant role. Endocrine disruptors, such as bisphenol A (BPA), phthalates, and pesticides, can mimic or block the action of sex hormones. Exposure to these substances in early childhood, which is increasingly common in the modern world, is considered another possible factor contributing to the shift in the age of puberty.

Biochemical and clinical signals

Clinical signs of early puberty include the development of breasts or testicles, rapid growth, the appearance of pubic hair, and behavioral changes.

Laboratory diagnostics is based on the measurement of basal and stimulated concentrations of LH, FSH, and sex hormones. The GnRH stimulation test is the gold standard in diagnostics for distinguishing between central and peripheral precocious puberty. Central precocious puberty occurs due to premature activation of the hypothalamic-pituitary-gonadal axis, which is manifested by increased secretion of GnRH, LH, and FSH. In contrast, peripheral precocious puberty is GnRH-independent and results from the autonomous production of sex hormones from the gonads or adrenal glands. Distinguishing these two forms is crucial for the diagnostic and therapeutic approach. This test uses gonadotropin-releasing hormone (GnRH) and measures the concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In central precocious puberty, there is a marked increase in LH, which, together with an LH/FSH ratio greater than 1, indicates activation of the hypothalamic-pituitary-gonadal axis. In peripheral precocious puberty, the LH response to GnRH is weak or absent.

The cost of early maturation

Early puberty can have significant health and psychosocial consequences. Precocious puberty accelerates growth, but possible early closure of the epiphyseal plates can ultimately result in shorter stature. Furthermore, the risk of developing metabolic syndrome, diabetes mellitus, and cardiovascular disease in adulthood is increased. Earlier and longer exposure to sex hormones can increase the risk of hormone-dependent cancers, such as breast and endometrial cancer. Psychosocial consequences are also a major concern today. Children who enter puberty before their peers may experience emotional difficulties, body image issues, and a higher risk of anxiety and depression.

A natural trend or a public health issue?

The decrease in the age of pubertal onset can be positively explained by improvements in living conditions and nutrition, representing a natural adaptive response of the organism. However, considering the consequences in adulthood, earlier puberty represents an increasing public health challenge. Education of parents, pediatricians, and teachers about the early signs of puberty and psychological support is needed, as well as the development of strategies to reduce exposure to endocrine disruptors. Preventive measures include the promotion of healthy nutrition, physical activity and the reduction of obesity in the child population. Furthermore, future research into the molecular mechanisms of pubertal regulation and the identification of biomarkers for early diagnosis is desirable.

Translated by: Mirta Maršić