A 12-day-old female infant presents with vomiting, poor feeding, dehydration, sodium 124 mEq/L, potassium 6.8 mEq/L, and hypoglycaemia. Examination shows clitoromegaly with fused labioscrotal folds. Which single test best confirms the diagnosis?
- A Plasma renin activity
- B Serum 17-hydroxyprogesterone ✓
- C Karyotype
- D Serum androstenedione
Correct answer: B. Serum 17-hydroxyprogesterone
Explanation
Salt-wasting congenital adrenal hyperplasia due to 21-hydroxylase deficiency shunts steroid precursors into the androgen pathway, producing virilisation in a genetic female plus mineralocorticoid deficiency with hyponatraemia and hyperkalaemia. Markedly elevated 17-hydroxyprogesterone is the diagnostic hallmark. Karyotype confirms 46,XX but does not identify the enzyme block, andrenin and androstenedione are elevated but non-specific. Treatment is hydrocortisone plus fludrocortisone and salt supplementation.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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