A 7-year-old boy has bilateral testicular volumes of 6 mL, Tanner stage 2 pubic hair, and accelerated growth velocity. Bone age is 9 years, and a GnRH stimulation test shows a pubertal LH response confirming gonadotropin-dependent puberty. Which investigation is essential next?
- A MRI of the brain with contrast to look for a CNS lesion ✓
- B Serum beta-hCG and alpha-fetoprotein levels
- C Testicular ultrasound to exclude a tumour
- D Adrenal CT scan to exclude congenital adrenal hyperplasia
Correct answer: A. MRI of the brain with contrast to look for a CNS lesion
Explanation
Unlike in girls, where most gonadotropin-dependent precocious puberty is idiopathic, central precocious puberty in boys has an organic CNS cause in a substantial proportion, including hypothalamic hamartoma, hydrocephalus, and suprasellar tumours. Therefore contrast MRI of the brain is mandatory in every boy with confirmed central precocious puberty. Testicular ultrasound and tumour markers address peripheral causes, which are excluded by the pubertal LH response, and adrenal pathology drives gonadotropin-independent virilization.
Reference: Williams Textbook of Endocrinology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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