What are the physical signs of precocious puberty in boys?

Updated: Mar 11, 2020
  • Author: Paul B Kaplowitz, MD, PhD; Chief Editor: Robert P Hoffman, MD  more...
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Precocious puberty in boys

  • The earliest sign of central precocious puberty (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 (eg, 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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