Precocious puberty

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Definition & Cutoffs - Too Fast, Too Young

  • Definition: Onset of secondary sexual characteristics (SSCs) before the accepted lower age limit.

  • Age Cutoffs:

    • Girls: < 8 years
    • Boys: < 9 years
  • Classification:

    • Central (True/GnRH-dependent): Premature activation of the hypothalamic-pituitary-gonadal (HPG) axis.
    • Peripheral (Pseudo/GnRH-independent): Excess sex hormones from gonads, adrenals, or exogenous sources.

⭐ The most common form of precocious puberty is idiopathic Central Precocious Puberty (CPP), and it is much more frequent in girls (approx. 10:1 girl-to-boy ratio).

Classification - Brain vs. Body Hormones

  • Central (GnRH-dependent): True, complete puberty from premature activation of the Hypothalamic-Pituitary-Gonadal (HPG) axis.
  • Peripheral (GnRH-independent): Pseudopuberty from sex hormones produced outside the brain/pituitary control loop (e.g., adrenals, gonads, external sources).

Hypothalamic-Pituitary Axis and Target Organs

⭐ While Central Precocious Puberty (CPP) is most often idiopathic in girls, a boy with CPP has a much higher likelihood of an underlying CNS lesion, mandating a brain MRI.

📌 Mnemonic: Central = CNS problem. Peripheral = Problem in the Physique (gonads/adrenals).

Diagnostic Workup - The Hormone Hunt

  • Initial Steps:

    • Bone Age: First-line investigation. X-ray of the left hand and wrist. Bone age is typically advanced >2 years beyond chronological age.
    • Hormonal Assay: Basal LH, FSH, estradiol (girls) or testosterone (boys). A basal LH > 0.3 IU/L is highly suggestive of Central Precocious Puberty (CPP).
  • Confirmatory Test:

    • GnRH Stimulation Test: The gold standard to differentiate CPP from Peripheral Precocious Puberty (PPP).
    • Pubertal Response (CPP): Peak LH > 5-8 IU/L and a peak LH/FSH ratio > 0.66.

⭐ The GnRH stimulation test is the definitive investigation to differentiate between GnRH-dependent (central) and GnRH-independent (peripheral) precocious puberty.

Algorithm for diagnosing precocious puberty in boys

Management - Pumping the Brakes

Central (CPP): Goal is to ↓ GnRH pulses & preserve adult height.

  • DOC: Long-acting GnRH analogs (continuous stimulation → downregulation).
    • Leuprolide acetate (monthly/3-monthly depot).
    • Triptorelin, Histrelin implant.
  • Monitor: ↓ Growth velocity & slowing of bone age advancement.

Peripheral (PPP): Address the specific underlying cause.

  • McCune-Albright: Aromatase inhibitors (Letrozole).
  • Testotoxicosis: Anti-androgens + Aromatase inhibitors.

⭐ GnRH agonist therapy initially causes a transient flare-up of puberty (↑ LH/FSH) before downregulation and suppression.

High-Yield Points - ⚡ Biggest Takeaways

  • Secondary sexual characteristics before age 8 in girls & 9 in boys.
  • Central (GnRH-dependent) shows a pubertal LH response to GnRH stimulation; peripheral (GnRH-independent) does not.
  • The first investigation is bone age assessment, which is typically advanced.
  • Central form is mostly idiopathic in girls; suspect CNS pathology in boys.
  • Key peripheral causes include McCune-Albright syndrome and adrenal or gonadal tumors.
  • Treatment for the central form is GnRH agonists (e.g., Leuprolide).

Practice Questions: Precocious puberty

Test your understanding with these related questions

A 6-year-old girl is brought to the pediatrician by her father for an annual physical examination. The father reports that the patient is a happy and healthy child, but he sometimes worries about her weight. He says that she is a “picky” eater and only wants chicken nuggets and French fries. He also notes some mild acne on her cheeks and forehead but thinks it’s because she “doesn’t like baths.” The father says she has met all her pediatric milestones. She has recently started kindergarten, can tell time, and is beginning to read. Her teacher says she gets along with her classmates well. The patient was born at 38 weeks gestation. She has no chronic medical conditions and takes only a multivitamin. Height and weight are above the 95th percentile. Physical examination reveals scattered comedones on the patient’s forehead and bilateral cheeks. There is palpable breast tissue bilaterally with raised and enlarged areolae. Scant axillary hair and coarse pubic hair are also noted. A radiograph of the left hand shows a bone age of 9 years. Serum follicular stimulating hormone (FSH) level is 9.6 mU/mL (normal range 0.7-5.3 mU/mL) and luteinizing hormone (LH) level is 6.4 mU/mL (normal range < 0.26 mU/mL). Which of the following is the most appropriate diagnostic test?

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Flashcards: Precocious puberty

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Constitutional delay of growth and puberty is quantified by _____ radio-graphic studies of the left hand and wrist

TAP TO REVEAL ANSWER

Constitutional delay of growth and puberty is quantified by _____ radio-graphic studies of the left hand and wrist

bone age

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