🌱 Chapter 42: Disorders of Puberty

Nelson's Pediatric Symptom-Based Diagnosis | Precocious Puberty · Delayed Puberty · Tanner Staging · Central vs Peripheral Precocious Puberty · Hypogonadotropic Hypogonadism · Hypergonadotropic Hypogonadism

🔍 Disorders of Puberty: Key Concepts

📊 Puberty Norms
Girls: breast development (thelarche) 8-13y, menarche ~2-2.5y after. Boys: testicular enlargement (>4 mL) 9-14y. Tanner staging 1-5.
⚡ Central Precocious Puberty (CPP)
GnRH-dependent, early activation of hypothalamic-pituitary-gonadal axis. More common in girls. Often idiopathic (girls) vs CNS lesion (boys). GnRH agonist treatment.
🔄 Peripheral Precocious Puberty (PPP)
GnRH-independent (sex steroids from adrenal, gonad, or exogenous). Causes: McCune-Albright, congenital adrenal hyperplasia, testotoxicosis, adrenal tumor.
⏳ Delayed Puberty
No breast development by 13y or menarche by 16y (girls); no testicular enlargement by 14y (boys). Constitutional delay (most common), hypogonadotropic (functional, CNS), hypergonadotropic (Turner, Klinefelter).
🧬 Hypergonadotropic Hypogonadism
High FSH/LH, low sex steroids. Causes: Turner syndrome (45,X), Klinefelter (47,XXY), gonadal dysgenesis, chemotherapy/radiation.
🧠 Hypogonadotropic Hypogonadism
Low/normal FSH/LH, low sex steroids. Causes: constitutional delay (most common), Kallmann syndrome (anosmia), pituitary/hypothalamic lesions, chronic disease, anorexia.

💡 Key takeaway: Central precocious puberty = GnRH-dependent (idiopathic vs organic). Peripheral = sex steroid-secreting tumor, CAH, McCune-Albright. Delayed puberty: constitutional delay vs hypogonadism; check bone age, FSH/LH, and consider imaging for CNS tumors.

🩺 Clinical Approach to Disorders of Puberty

🔹 Step 1: Define abnormal timing
• Precocious: breast development <8y (girls) or testicular enlargement <9y (boys).
• Delayed: no breast by 13y, no menarche by 16y (girls); no testicular enlargement by 14y (boys).
🔹 Step 2: Differentiate central vs peripheral precocious puberty
• Central (CPP): GnRH-dependent, progressive, symmetric, bone age advanced, LH-predominant response to GnRH stimulation.
• Peripheral (PPP): GnRH-independent, may be asymmetric, sex steroid elevated but low/normal LH. Causes: McCune-Albright (café-au-lait, polyostotic fibrous dysplasia), CAH (17-OHP elevated), testotoxicosis (boys), adrenal/ovarian tumor.
🔹 Step 3: Evaluate delayed puberty
• Bone age: delayed = constitutional delay vs hypogonadism.
• FSH/LH: low = hypogonadotropic; high = hypergonadotropic.
• Hypogonadotropic: constitutional delay (most common), chronic disease, Kallmann (anosmia), pituitary tumor, anorexia.
• Hypergonadotropic: Turner (girls), Klinefelter (boys), gonadal failure.
🔹 Step 4: Key diagnostic tests
• Bone age X-ray (left hand/wrist).
• GnRH stimulation test: peak LH >5-8 IU/L = central precocious puberty.
• Basal LH, FSH, estradiol/testosterone, DHEA-S, 17-OHP.
• Pelvic ultrasound (girls: ovarian/uterine size).
• Brain MRI (CPP in boys, rapid progression, age <6y, neurologic signs).
🔹 Step 5: Treatment overview
• CPP: GnRH agonists (leuprolide) slow progression, preserve adult height.
• PPP: treat underlying cause (surgery for tumor, hydrocortisone for CAH, aromatase inhibitors/testolactone).
• Constitutional delay: reassurance, observation; consider low-dose sex steroids if psychosocial distress.
• Hypogonadism: sex steroid replacement (estrogen/testosterone), treat underlying cause.