The age of onset of puberty can vary. It starts earlier in girls than in boys. Some specialists think it that if by the age of 13 for girls and 15 for boys no signs of starting puberty then they should be referred to a specialist doctor, usually an endocrinologist.

There is an article on the normal stages of puberty elsewhere on this site. In general any girl who has not had their first period or a boy showing any testicular development by the age of 15 should be investigated for a delay of puberty.

In boys the testes should have descended in the scrotum before or just after birth. Un-descended testes (cryptorchidism) is a not an uncommon event in boys and can be easily rectified with drugs or surgery. A history of bilateral cryptorchidism (both testes undescended) should alert doctors to the possibility of a problem with puberty later, but this does not necessarily mean that a boy with cryptorchadism will develop Kallmann’s.