Precocious Puberty — High-Yield Exam Summary

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Precocious puberty = appearance of secondary sexual characteristics before 8 years in girls or 9 years in boys.

First Distinguish Central from Peripheral

Central Precocious Puberty (CPP) — GnRH-dependent

  • Premature activation of the hypothalamic–pituitary–gonadal (HPG) axis
  • ↑ GnRH → ↑ LH/FSH → ↑ sex steroids
  • Puberty generally progresses in the normal sequence, but too early
  • Pubertal LH response to GnRH/GnRH-agonist stimulation
  • Growth velocity and bone age are usually increased

Peripheral Precocious Puberty — GnRH-independent

  • Sex steroids are produced without activation of the HPG axis
  • LH/FSH remain prepubertal/suppressed
  • Pubertal development may be discordant or atypical
  • Causes include gonadal, adrenal, tumor-related, or exogenous sex-steroid production

Causes of Central Precocious Puberty

Girls

  • Idiopathic — most common
  • CNS lesions/tumors
  • Hypothalamic hamartoma
  • Previous CNS irradiation, surgery, or trauma
  • CNS infection/inflammation
  • Rare genetic causes, e.g. MKRN3-related familial CPP

Boys

  • CNS pathology is more likely than in girls
  • Hypothalamic hamartoma
  • CNS tumors/lesions
  • Previous CNS irradiation, surgery, or trauma
  • CNS infection/inflammation
  • Idiopathic CPP can occur, but is less common than in girls

Causes of Peripheral Precocious Puberty

Estrogen excess

  • Ovarian follicular cysts
  • Granulosa-cell ovarian tumor
  • McCune–Albright syndrome
  • Exogenous estrogen

Androgen excess

  • Congenital adrenal hyperplasia — especially 21-hydroxylase deficiency
  • Adrenal tumor
  • Testosterone-producing testicular (Leydig cell) tumor
  • Familial male-limited precocious puberty (testotoxicosis)
  • β-hCG–secreting tumors
  • Exogenous androgen exposure

Exam Clues

  • Pubertal LH → Central

 

  • Suppressed LH + high sex steroid → Peripheral

 

  • Precocious puberty in a boy → strongly consider CNS pathology

 

  • Café-au-lait spots + precocious puberty → McCune–Albright syndrome

 

  • Virilization + high androgen → CAH/adrenal or gonadal source

 

  • Testosterone high + LH suppressed in a boy → peripheral testosterone source

 

  • Rapid growth + advanced bone age → significant sex-steroid exposure

 

  • Breast development alone in a young girl, without growth acceleration or advanced bone age → consider premature thelarche rather than true precocious puberty

 

  • Pubic hair/body odor alone → consider premature adrenarche

One-Line MCQ Approach

Early puberty → ask “Is the LH/HPG axis ON?” Pubertal LH = CENTRAL | Suppressed LH = PERIPHERAL → then identify the source.

A new Endocrine Society clinical practice guideline, released June 2026, refines when brain MRI is indicated in confirmed CPP:

  • Routine brain MRI is not recommended in girls aged 6.0–8.0 years or boys aged 8.0–9.0 years with confirmed CPP and no CNS symptoms or signs.
  • Brain MRI remains important for:
    • Any child with neurological symptoms/signs
    • Girls with onset younger than 6 years
    • Boys with onset younger than 8 years, given the higher baseline likelihood of CNS pathology in boys
  • The guideline also favors ultrasensitive basal LH testing as a first-line diagnostic tool and supports a period of watchful observation (physical exams every 4–6 months) in select girls with early, slowly progressive breast development, rather than immediate full work-up.
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