Harvey's Garden

Precocious Puberty

2 min read

  • Definition
    • Development of secondary sexual characteristics before age 8 in girls and 9 in boys.
    • Advanced Bone Age: Bone age > Chronological age (indicates significant hormonal effect).
  • Initial Workup
    • Bone Age Assessment (Best Initial Step): X-ray of left hand and wrist.
      • If Normal (Bone Age ≈ Chronological Age): Benign variants (Premature Thelarche or Premature Adrenarche). No further workup needed; reassure.
      • If Advanced (Bone Age > Chronological Age): Pathologic. Proceed to GnRH stimulation test (or check basal LH).
  • Classification & Etiology
    • Central Precocious Puberty (GnRH-Dependent)
      • Mechanism: Premature activation of the Hypothalamic-Pituitary-Gonadal (HPG) axis.
      • Labs: High basal LH or ↑ LH in response to GnRH stimulation.
      • Etiology:
        • Idiopathic: Most common cause in females (approx. 80%).
        • CNS Lesions: Most common cause in males (e.g., Hypothalamic Hamartoma, Astrocytoma, Pinealoma, Hydrocephalus).
          • Note: Hypothalamic hamartomas are associated with gelastic seizures (laughing spells).
    • Peripheral Precocious Puberty (GnRH-Independent)
      • Mechanism: Autonomous secretion of sex steroids (estrogen/testosterone) independent of HPG axis.
      • Labs: Low basal LH and no LH increase (blunted response) to GnRH stimulation (feedback inhibition by high peripheral hormones).
      • Etiology:
        • McCune-Albright Syndrome: Triad of precocious puberty, café-au-lait spots (“coast of Maine” borders), and fibrous dysplasia of bone. Mutation in G-protein signaling (GNAS).
        • Congenital Adrenal Hyperplasia (CAH): Late-onset (non-classic) 21-hydroxylase deficiency.
        • Tumors:
          • Girls: Granulosa cell tumor (Ovary).
          • Boys: Leydig cell tumor (Testis).
        • Exogenous exposure: Sex steroids.
  • Diagnostics Summary (Algorithm)
    1. X-ray Wrist (Bone Age):
      • Normal → Isolated Thelarche/Adrenarche.
      • Advanced → Check Basal LH.
    2. Basal LH:
      • High → Central PP.
      • Low → GnRH Stimulation Test.
    3. GnRH Stimulation Test:
      • ↑ LH → Central PP → MRI Brain (r/o tumor).
      • No change in LH → Peripheral PP → US Pelvis/Adrenals, check 17-OHP, Testosterone, Estradiol.
  • Treatment
    • Central PP:
      • Continuous GnRH Agonists (e.g., Leuprolide, Goserelin).
      • Mechanism: Constant stimulation desensitizes pituitary GnRH receptors → ↓ FSH/LH release.
    • Peripheral PP:
      • Treat underlying cause (e.g., tumor resection).
      • McCune-Albright: Aromatase inhibitors (Letrozole, Anastrozole) or Tamoxifen to block estrogen effects; Ketoconazole (anti-androgen) in males.

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