A 14-year-old boy is referred for tall stature, long limbs, gynaecomastia, sparse pubic hair, small firm testes (2 mL volume), and azoospermia. His IQ is normal. Karyotype is 47,XXY. Testosterone is low, FSH and LH are markedly elevated. Which statement about the pathophysiology is CORRECT?
- A Hyalinisation and fibrosis of the seminiferous tubules leads to primary gonadal failure with elevated gonadotrophins ✓
- B The XXY karyotype causes failure of Leydig cell development, with absent testosterone from birth
- C The additional X chromosome suppresses LH receptors on Leydig cells, causing secondary hypogonadism
- D Gynecomastia in Klinefelter syndrome is due to excess testosterone aromatization caused by abnormal adipose tissue
Correct answer: A. Hyalinisation and fibrosis of the seminiferous tubules leads to primary gonadal failure with elevated gonadotrophins
Explanation
Klinefelter syndrome (47,XXY) is characterised by progressive hyalinisation and fibrosis of the seminiferous tubules (germ cell depletion) and Leydig cell dysfunction, causing primary testicular failure. This results in low testosterone, hypergonadotropic hypogonadism (high FSH, LH), small firm testes, azoospermia, and gynaecomastia (due to low testosterone-to-oestrogen ratio). Leydig cells are present but become fibrotic over time. The process accelerates around puberty. This is a primary gonadal failure, not secondary (hypothalamic-pituitary) failure.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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