Puberty and Its Disorders

Normal Puberty - The Hormone Symphony

Puberty: A neuroendocrine cascade driven by pulsatile Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus. Influenced by genetics, nutrition (Leptin: permissive), and Kisspeptin.

• Core Pathway (Gonadarche):
  • Hypothalamus: Pulsatile GnRH release.
  • Anterior Pituitary: Secretes LH & FSH.
  • Gonads (Ovaries/Testes): Produce sex steroids (Estrogen-♀ / Testosterone-♂) under LH/FSH stimulation.
  • Effects: Development of secondary sexual characteristics, growth spurt, achievement of fertility.
• Adrenarche:
  • Separate adrenal androgen (DHEA, DHEAS) surge around 6-8 years.
  • Contributes to pubic/axillary hair (pubarche), body odor, acne.

⭐ The first sign of puberty in girls is thelarche (breast budding); in boys, it's testicular enlargement (≥ 4ml or > 2.5cm length).

Precocious Puberty - Early Bloomers

• Definition: Onset of secondary sexual characteristics before age 8 in girls, 9 in boys.
• Types:
  • Central (GnRH-dependent): Premature activation of Hypothalamic-Pituitary-Gonadal (HPG) axis.
    • Idiopathic (most common, esp. girls).
    • CNS lesions: Hamartoma (most common tumor), astrocytoma, hydrocephalus.
  • Peripheral (GnRH-independent): Excess sex steroids from gonads, adrenals, or exogenous sources.
    • Girls: Ovarian cysts/tumors.
    • Boys: Leydig cell tumors, Congenital Adrenal Hyperplasia (CAH), HCG-secreting tumors.
    • McCune-Albright Syndrome (MAS).
• Incomplete variants: Premature thelarche, premature adrenarche/pubarche.
• Diagnosis:
  • Advanced bone age (X-ray hand/wrist).
  • GnRH stimulation test: Differentiates Central (LH surge) from Peripheral (suppressed LH). Peak LH >5-8 IU/L; LH/FSH ratio >0.6.
  • Pelvic/Testicular USG. Brain MRI for Central PP (esp. boys & girls <6 yrs).
• Treatment:
  • Central: GnRH analogs (e.g., Leuprolide).
  • Peripheral: Address underlying cause.

⭐ McCune-Albright Syndrome triad:

1. Peripheral precocious puberty.
2. Café-au-lait macules (irregular "coast of Maine" border).
3. Polyostotic fibrous dysplasia.

Delayed Puberty - Late to the Party

• Definition:
  • Girls: No breast development (thelarche) by 13 years; no menarche by 16 years or >5 years after thelarche.
  • Boys: No testicular enlargement (testicular volume <4 mL or longest diameter <2.5 cm) by 14 years.
• Most common: Constitutional Delay of Growth & Puberty (CDGP) - "late bloomers"; delayed bone age, positive family history.
• Classification & Key Causes:
  • Hypogonadotropic Hypogonadism (Central; ↓FSH/LH):
    • Functional: Chronic illness, malnutrition, hypothyroidism, intense exercise.
    • Congenital: Kallmann syndrome (anosmia), Prader-Willi.
    • Acquired: CNS tumors (e.g., craniopharyngioma).
  • Hypergonadotropic Hypogonadism (Primary Gonadal Failure; ↑FSH/LH):
    • Girls: Turner syndrome (45,XO).
    • Boys: Klinefelter syndrome (47,XXY).
    • Other: Gonadal dysgenesis, post-chemo/radiation.
• Initial Evaluation: History, exam (Tanner staging), bone age. Then FSH, LH, Estradiol/Testosterone.

⭐ Kallmann syndrome: Defective GnRH neuron migration leading to hypogonadotropic hypogonadism and anosmia/hyposmia. Often KAL1 gene mutation.

High‑Yield Points - ⚡ Biggest Takeaways

• Tanner staging is crucial for pubertal assessment.
• Precocious puberty: onset <8 years (girls), <9 years (boys).
• Delayed puberty: no signs by 13 years (girls), 14 years (boys).
• McCune-Albright syndrome: triad of precocious puberty, café-au-lait spots, polyostotic fibrous dysplasia.
• Kallmann syndrome: hypogonadotropic hypogonadism plus anosmia.
• Constitutional delay (CDGP): most common cause of delayed puberty in boys.
• Central precocious puberty is GnRH-dependent; peripheral is GnRH-independent.