✅ Model Answer:
• Diagnosis: Hypogonadotropic hypogonadism (normosmic) – congenital GnRH deficiency.
• Evidence: 46,XY, delayed puberty, micropenis, bilateral cryptorchidism, low LH/FSH, low testosterone, normal sense of smell, normal MRI pituitary.
• Next step: Start testosterone replacement therapy (to induce puberty). For fertility: GnRH pump or gonadotropins (hCG + FSH). Genetic testing (GNRHR, KISS1R, TAC3, TACR3, PROKR2, PROK2). Multidisciplinary care.

✅ Model Answer:
• Definition: Hypogonadotropic hypogonadism (HH) due to GnRH deficiency – can be normosmic or with anosmia (Kallmann syndrome).
• Genes involved:
- Normosmic HH: GNRHR, GNRH1, KISS1R, TAC3, TACR3, PROKR2, PROK2, CHD7, FGF8/FGFR1, NSMF.
- Kallmann syndrome (anosmic HH): ANOS1 (KAL1), FGFR1, PROKR2, PROK2, CHD7, FGF8, WDR11, SOX10.
• Inheritance: X-linked (ANOS1), autosomal dominant, autosomal recessive, or oligogenic.
• Pathophysiology: Defective migration of GnRH neurons from the olfactory placode to the hypothalamus → inadequate GnRH secretion → low LH/FSH → low sex steroids.
• Prevalence: 1 in 10,000-100,000 (males more commonly affected).

✅ Model Answer:
• Neonatal/Childhood:
- Micropenis: Penile length <2.5 cm (SD) in term infants.
- Bilateral cryptorchidism.
- Undescended testes.
• Adolescence:
- Delayed puberty: No testicular enlargement (<4 mL), no pubic hair, no growth spurt by age 14.
- Eunuchoid proportions: Tall stature (arm span > height), increased lower segment.
- Small testes.
- Gynecomastia (if androgen deficiency).
- Anosmia/hyposmia (if Kallmann syndrome).
- Low bone density.
• Other: Fatigue, low energy, infertility.

✅ Model Answer:
• Karyotype: 46,XY (to rule out Klinefelter).
• Hormonal studies:
- LH/FSH: Low or inappropriately normal (in the setting of low testosterone).
- Testosterone: Low.
- Prolactin: Normal (rule out hyperprolactinemia).
- Estradiol: Low.
- Inhibin B: Low (if puberty has not started).
• Sense of smell: Olfactory testing (to differentiate Kallmann from normosmic HH).
• MRI brain/pituitary: Normal (excludes pituitary tumors, stalk lesions).
• Genetic testing: GNRHR, KISS1R, TAC3, TACR3, PROKR2, PROK2, ANOS1, FGFR1, etc.
• Bone age: Delayed.
• Testicular ultrasound: To locate undescended testes.

✅ Model Answer:
• Testosterone replacement (for puberty induction):
- IM testosterone esters: 50 mg/month initially, increasing to 100-250 mg every 2-4 weeks (adult dose).
- Transdermal testosterone: 2.5-5 mg/day (gel or patch).
- Duration: Lifelong (unless fertility is desired).
• Fertility (if desired):
- GnRH pump: Intermittent subcutaneous GnRH (to stimulate LH/FSH).
- Gonadotropins: hCG (acts as LH) + FSH (or human menopausal gonadotropin – HMG).
- Spermatogenesis: Usually achieved within 6-24 months.
• Monitoring:
- Testosterone levels.
- Growth and bone age.
- Bone density.
- Testicular size (for fertility).
• Psychosocial support.

✅ Model Answer:
• Infertility: Without treatment, spermatogenesis does not occur.
• Osteoporosis: Due to lack of sex steroids (if untreated).
• Undescended testes: Increased risk of testicular malignancy, hernia.
• Psychosocial: Delayed puberty, body image, self-esteem issues.
• Kallmann syndrome: Associated with midline defects (cleft palate, renal agenesis, color blindness, cerebellar ataxia, mirror movements).
• Bone health: Fracture risk if untreated.

✅ Model Answer:
• Prognosis:
- Good with testosterone replacement and fertility treatment.
- Puberty: Can be induced successfully with testosterone.
- Fertility: 70-80% achieve spermatogenesis with GnRH pump or gonadotropins.
- Quality of life: Normal with treatment.
- Life expectancy: Normal.
• Long-term follow-up:
- Monitor testosterone levels.
- Monitor bone density.
- Monitor for testicular malignancy (if cryptorchidism).
- Psychosocial support.
- Genetic counseling.

✅ Model Answer:
• Hypogonadotropic hypogonadism (normosmic):
- Sense of smell: Normal.
- Genes: GNRHR, KISS1R, TAC3, TACR3, PROKR2, PROK2, etc.
- Associated features: Usually isolated hypogonadism.
- MRI: Normal olfactory bulbs.
• Kallmann syndrome:
- Sense of smell: Anosmia or hyposmia.
- Genes: ANOS1 (KAL1), FGFR1, PROKR2, PROK2, CHD7, FGF8, WDR11, SOX10.
- Associated features: Midline defects (cleft palate, renal agenesis, color blindness, cerebellar ataxia, mirror movements, hearing loss).
- MRI: Absent or hypoplastic olfactory bulbs and sulci.
• Both: Low LH/FSH, low testosterone, delayed puberty, micropenis, cryptorchidism.
• Treatment: Same (testosterone replacement, GnRH pump, gonadotropins for fertility).