What are the physical signs of precocious puberty in boys?

Updated: Nov 30, 2020
  • Author: Paul B Kaplowitz, MD, PhD; Chief Editor: Robert P Hoffman, MD  more...
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The earliest sign of CPP is enlargement of the testes, which depends on increased production of follicle-stimulating hormone (FSH); testicular length is more than 2.5 cm, or testicular volume (with Prader orchidometer beads) is 4 mL or more. If progressive signs of androgen excess occur in a boy without increased testicular size, consider possible causes of precocious pseudopuberty, including congenital adrenal hyperplasia, familial male precocious puberty, and Leydig-cell tumors (a testicular nodule is usually palpable). Human chorionic gonadotropin (HCG)–secreting tumors somewhat increase testicular size by stimulating testicular Leydig-cell LH receptors.

Other signs of puberty (eg, penis growth, reddening and thinning of the scrotum, increased pubic hair) are a consequence of increased testosterone production and occur within 1-2 years after testicular enlargement.

Pubic hair growth that occurs without penis and testicular enlargement and other signs of increased androgen production indicate a condition such as premature adrenarche or a mild, nonclassic form of congenital adrenal hyperplasia rather than true puberty.

Later signs of puberty include the pubertal growth spurt, acne, voice change, and facial hair.

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