4 - Abnormal puberty

Summary

Precocious puberty

Precocious onset of puberty is defined as occurring younger than two standard deviations before the average age, which is less than eight years old in females (compared with less than nine years in males). Thus, in many girls early-onset of puberty merely represents one end of the normal distribution. However, a number of pathological conditions may prematurely activate the GnRH-LH/FSH axis, resulting in the precocious onset of puberty. Furthermore, certain physical secondary sexual features (e.g. virilisation without breast development) may occur in the absence of ‘true puberty’ (i.e. absent hypothalamic-pituitary activation) due to abnormal peripheral secretion of sex steroids.

CAUSES OF PRECOCIOUS PUBERTY

Gonadotrophin-dependent (‘true’ or ‘central’ precocious puberty):

1. • Idiopathic (family history, overweight/obese)

2. • Intracranial lesions (tumours, hydrocephalus, irradiation, trauma)

3. • Gonadotrophin-secreting tumours

4. • Hypothyroidism

Variants:

1. • Premature thelarche (and thelarche variant)

2. • Adrenarche

Gonadotrophin-independent:

1. • Congenital adrenal hyperplasia

2. • Sex steroid-secreting tumours (adrenal or ovarian)

3. • McCune-Albright syndrome

4. • Exogenous estrogen ingestion/administration

TRUE PRECOCIOUS PUBERTY

The appearance of pubertal physical features follows the normal sequence (‘consonance’) beginning with breast development. The diagnosis is made by the finding of elevated basal gonadotrophin levels and, after stimulation with intravenous GnRH, the serum LH concentration is higher than FSH. It is important to consider intracranial pathology and arrange imaging if indicated.

PREMATURE THELARCHE

Premature breast development in the absence of other signs of puberty may present at any age from infancy.