In over 90% of cases, delayed puberty is due to what is known as a constitutional delay in growth and puberty. This means it occurs in children who are healthy but simply have a slower rate of physical development than average. Typically these children will have a short stature compared with other children of the same age and they are often thin and have a family history of delayed puberty. Sometimes delayed puberty and growth can be secondary to a chronic illness, malnutrition, excessive physical exercise and even stress. For example, diabetes, cystic fibrosis and coeliac disease can delay pubertal development while excessive exercise and anorexia, where the proportion of body fat is very low, can also delay puberty.

Rare causes of delayed or absent puberty can be caused by loss of hormone secretions from the hypothalamus and pituitary gland or by disorders of the testes or ovaries. 

Puberty is initiated by increasing the production of luteinising hormone and follicle stimulating hormone (gonadotrophins) from the pituitary gland, which is driven by increasing release of gonadotrophin-releasing hormone from the hypothalamus. When something goes wrong with this control, then hypogonadotrophic delayed puberty occurs; hypogonadotrophic meaning low levels of gonadotrophins. Some forms of gonadotrophin deficiency are caused by genetic defects, for example, Kallman’s syndrome, or alternatively the deficiency can be acquired as a result of a tumour, trauma, surgery or radiation therapy of the head.

Disorders of the testes or ovaries can cause hypergonadotrophic delayed puberty. In this case, levels of gonadotrophins are high, but the ability of the testes or ovaries to detect this is impaired and therefore they cannot respond to the gonadotrophins by producing testosterone and oestrogens, respectively. Chromosomal disorders such as Klinefelter’s syndrome in boys and Turner syndrome in girls result in abnormal development of the testes and ovaries with reduced or absent production of testosterone or oestrogen. Other gonadal disorders include failure of the testes to descend (cryptorchidism), testicular torsion, irradiation of the pelvic/abdominal area, gonadal surgery and mumps (although mumps rarely causes pre-pubertal damage to the testes).