Precocious Puberty in Boys

Key Features

• Puberty is considered precocious in boys if secondary sexual characteristics appear before age 9 years

• While the frequency of central precocious puberty is much lower in boys than girls, boys are more likely to have an associated CNS abnormality

• In addition, several types of gonadotropin-independent (peripheral) precocious puberty occur in boys

Clinical Findings

• Increased linear growth rate and growth of pubic hair are the most common presenting signs

• Testicular size differentiates central precocity, in which the testes enlarge, from gonadotropin-independent causes, in which the testes usually remain small (< 2 cm in the longitudinal axis)

• In familial male precocious puberty and HCG-mediated precocious puberty, there may be some testicular enlargement

• Tumors of the testis are associated with either asymmetric or unilateral testicular enlargement

Diagnosis

• Elevated testosterone levels verify early pubertal status but do not differentiate the source

• Basal high-sensitivity serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations will be in the pubertal range in boys with central precocious puberty and the LH response to gonadotrophin-releasing hormone (GnRH) stimulation testing is pubertal

• Sexual precocity caused by congenital adrenal hyperplasia is usually associated with abnormal plasma adrenal androgens

• Serum β-HCG concentrations signify the presence of an HCG-producing tumor (eg, CNS dysgerminoma or hepatoma) in boys with precocious puberty and testicular enlargement but suppressed gonadotropins following GnRH testing

• In all boys with central precocious puberty, cranial MRI should be obtained to evaluate for a CNS abnormality

• If testing suggests peripheral precocious puberty and laboratory studies are not consistent with congenital adrenal hyperplasia, imaging may be useful in detecting hepatic, adrenal, and testicular tumors

Treatment

• Underlying cause should be treated

• GnRH analogs may be used

• Boys with McCune-Albright syndrome or familial testotoxicosis can be treated with

  • Agents that block steroid synthesis (ketoconazole)

  • A combination of antiandrogens (spironolactone) and aromatase inhibitors (anastrozole or letrozole) that block the conversion of testosterone to estrogen