PRECOCIOUS PUBERTY

Part of “CHAPTER 92 – PRECOCIOUS AND DELAYED PUBERTY“

The diagnosis of precocious puberty (PP) depends on a precise definition of the timing of normal puberty. It was previously accepted that normal puberty does not begin before age 8 years in girls and not before age 9 years in boys. A multicenter study of 17,077 girls revealed that the prevalence of breast development and/or pubic hair before age 8 years was 27% in black girls and 7% in white girls. By age 9 years, 48% of black girls and 15% of white girls showed some sign of pubertal development.1 Interestingly, the mean age of menarche, 12.2 years in black girls and 12.9 years in white girls, did not differ significantly from previous reports. Therefore, new guidelines have been recommended redefining PP in girls as the onset of breast and/or pubic hair development before 7 years in white and 6 years in black girls.2 Nonetheless, girls younger than 8 years old with rapid progression of puberty, poor adult height predictions, or psychosocial factors may still deserve evaluation and therapeutic intervention.
Long-term outcomes and therapeutic interventions differ depending on the etiology of premature pubertal development. Classic distinctions have been made between gonadotropin-dependent (i.e., central PP), gonadotropin-independent (i.e., peripheral PP), premature thelarche, and premature pubarche.

PREMATURE THELARCHE

Premature thelarche is isolated premature breast development without other signs of estrogenization, such as growth acceleration or bone age advancement. It is not uncommon in the first 1 to 4 years of life,3 with the peak prevalence in the first 2 years.4,5 Premature thelarche is distinct from neonatal breast hyperplasia, which is common in the first few months of life, results from high levels of gestational hormones and spontaneously resolves over a few months.

Breast enlargement in premature thelarche may be unilateral or bilateral and often has a waxing and waning course. Complete regression is usually seen only if the onset is before age 2 years.4,5 The etiology is unknown, but postulated mechanisms include abnormal sensitivity of breast tissue to small physiologic amounts of estrogen,6 small autonomously functioning estrogen-producing ovarian cysts,7 exogenous exposure to estrogens,8 delayed inactivation of the hypothalamic–pituitary–gonadal axis after infancy,4 or partial activation of GnRH neurons.9 Traditionally, premature thelarche has been considered self-limited and a variant of normal. However, long-term follow-up of large cohorts of girls with premature thelarche reveals a 14% to 18% incidence of progression to gonadotropin-dependent PP,5 which could not be predicted from clinical or laboratory features.

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