Puberty refers to the set of physiological changes by which a child’s body matures into an adult body with the biological features required for reproduction.

Puberty is regulated by the hypothalamus, the pituitary and the gonads, and these organs function in a coordinated way as the HPG axis. The adrenal glands are also involved, independently of the HPG axis, by secreting increased amounts of male sex hormones which induce pubic and underarm hair development in girls. First, the brain stimulates the hypothalamus to produce the gonadotrophin-releasing hormone, GnRH. The pituitary gland responds by producing two further hormones, luteinising hormone (LH) and follicle-stimulating hormone (FSH). These hormones then stimulate the gonads to produce estradiol (a hormone of the type known as estrogens) if they are ovaries and testosterone if they are testes, and these sex hormones orchestrate the physiological changes characteristic of puberty. The FSH and LH also stimulate the development of oocytes (eggs) in females and sperm in males.

While some of the hormonal pathways that regulate puberty are well understood, it remains unclear what triggers puberty in the first place.

Clearly, puberty is a complex physiological process involving a delicate balance of hormonal function. Therefore, a range of genetic variations affecting the structure, amounts or responses to hormones can upset the balance and lead to puberty that arrives early, late, not at all, not in the expected sequence, or out of step with the sex of the child. Further, some environmental chemicals are known or suspected to alter hormonal pathways that regulate puberty, perhaps explaining why the age of puberty has been decreasing in many countries.


Because this website deals primarily with variations of sex development that have a genetic basis and are detected in the newborn period, variations appearing at puberty are not dealt with further here.

Future editions will include expanded coverage of this topic.



Last updated: 19 September 2013

Edit history: Author P. Koopman 9/12; revised PK 5/13