Pathophysiology
Clinical meaning
Delayed puberty occurs when secondary sexual characteristics fail to develop at the expected age. In girls, this means no breast development by age 13 or no menarche by age 15. In boys, it means no testicular enlargement by age 14. The hypothalamic-pituitary-gonadal (HPG) axis normally activates during puberty, triggering the release of sex hormones that drive physical development. When this axis fails to activate on schedule or the gonads do not respond appropriately, puberty is delayed. Constitutional delay (a normal variant where puberty starts late but progresses normally) is the most common cause.