A 16-year-old boy is evaluated for absent pubertal development. He has tall stature (height >95th centile), long legs, and small firm testes (2 mL bilaterally). He has mild learning difficulties. Karyotype is 47,XXY. FSH is 42 IU/L and LH is 28 IU/L. Testosterone is low. What is the diagnosis?
- A Constitutional delay of growth and puberty
- B Kallmann syndrome
- C Klinefelter syndrome ✓
- D Primary hypothyroidism
Correct answer: C. Klinefelter syndrome
Explanation
Klinefelter syndrome (47,XXY) classically presents with tall stature, small firm testes, hypergonadotropic hypogonadism (elevated FSH and LH with low testosterone), and often mild learning or behavioral difficulties. Kallmann syndrome features low gonadotropins and anosmia with normal stature. Constitutional delay shows delayed bone age with low gonadotropins and eventual spontaneous puberty. Primary hypothyroidism does not cause hypergonadotropic hypogonadism.
Reference: Williams Textbook of Endocrinology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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