Definition and causes of precocious puberty
Pubertal development is unusual in females younger than 8 years and males younger than 9 years. Precocious puberty (early onset of puberty) may be gonadotrophin-dependent (central) or gonadotrophin-independent.
Central precocious puberty is defined as breast development in females younger than 8 years and testicular enlargement in males younger than 9 years. It is caused by activation of the hypothalamic–pituitary axis; this is often idiopathic, but can be caused by brain lesions such as tumours, cysts or inflammatory conditions.
Gonadotrophin-independent precocious puberty is much less common. It can cause early pubertal changes that are in keeping with the child’s primary sexual characteristics, but can also result in feminisation in males or virilisation in females. It arises from a range of conditions causing sex-hormone overproduction by the gonads or adrenal glands. These causes include ovarian cysts, ovarian tumours, testicular stromal and germ cell tumours; rare causes include severe primary hypothyroidism or genetic disorders such as McCune Albright syndrome1, testotoxicosis2 and congenital adrenal hyperplasia.
Precocious puberty is more common in females, in whom it is usually idiopathic, although specialist investigation to exclude a pathological cause must still be considered. In males, precocious puberty is more likely to have a pathological cause.
Precocious puberty is often confused with:
- Premature adrenarche: characterised by an early increase (before age 8 years) in adrenal androgens (eg dehydroepiandrosterone sulfate [DHEAS]), leading to acne, change in body odour and premature development of body hair, but no signs of central puberty (testicular development in males or breast development in females). This is the most common differential diagnosis of precocious puberty, especially in females.
- Premature thelarche: the early development of a small amount of breast tissue in females without a growth spurt or other pubertal signs. Breast tissue development before the age of 1 year is usually a normal variant, is common, and usually regresses. It requires specialist referral if it fails to regress, is progressive, is seen in females aged 2 years or older or if there are other concerns, such as rapid growth or other pubertal signs.
These two conditions require specialist referral, but unlike precocious puberty, the specialist assessment does not need to be undertaken urgently.