delayed puberty

Delayed puberty is the flip side of precocious puberty: the expected signs of sexual development have not begun by an age when most peers have started, typically by about 13 in girls and 14 in boys. The body's pubertal program is running behind schedule.

Causes fall into a few families. Most common, and reassuring, is constitutional delay, a normal late-blooming variant in which everything is intact but on a slow timetable. Otherwise the problem may be hypogonadotropic, where the brain fails to drive the gonads (low LH and FSH, as in Kallmann syndrome or chronic illness and undernutrition), or hypergonadotropic, where the gonads themselves cannot respond despite high LH and FSH (as in Turner or Klinefelter syndromes).

The pattern of LH and FSH is therefore the diagnostic fork in the road: low gonadotropins point upstream to the brain, while high gonadotropins point to gonadal failure. Bone age, growth history, sense of smell, and family history all help sort constitutional delay from a true deficiency.

An important practical caveat is that distinguishing simple constitutional delay from permanent hypogonadism can be genuinely hard in early adolescence, because both can look the same at first. Time, repeated assessment, and sometimes a short trial of low-dose sex hormones are used to clarify the picture rather than rushing to a label.