Puberty disorders typically fall into two categories: too early (precocious) or too late (delayed). Early puberty in girls is defined as either breast or pubic hair development before the age of 8yr. In boys, it is defined as testicular enlargement or pubic hair development before the age of 9yr. In addition, even if the timing is after 8 or 9yr, there may be an issue if the puberty is developing too quickly through the different stages (rapid tempo). The two reasons to intervene with early puberty are potential compromise in final adult height (as the growth plates prematurely close) and the psychosocial implications of going through these changes too soon. In rare cases, the early puberty may be due to a tumor (either in the pituitary gland or the testes/ovaries).
Late puberty is defined in boys as minimal physical changes over the age of 14yr. In girls, it is defined as no periods by age 14yr (borderline) to 16yr (delayed). These conditions may be due to an underlying genetic syndrome such as Klinefelter syndrome (boys) or Turner syndrome (girls). Alternatively, it may simply represent being a “late bloomer”, and the patients may catch-up either spontaneously or with the assistance of short-term hormone replacement therapy.
Turner syndrome society:
American Association for Klinefelter syndrome: