A 32-year-old asymptomatic man is found incidentally to have a serum calcium of 11.0 mg/dL with intact PTH of 78 pg/mL. His father had similar biochemistry. Twenty-four hour urinary calcium excretion is low, and the fractional excretion of calcium to creatinine clearance ratio is 0.008. What is the correct management?
- A No surgery, reassure and screen family members ✓
- B Four-gland exploration
- C Focused parathyroidectomy after sestamibi scan
- D Cinacalcet therapy lifelong
Correct answer: A. No surgery, reassure and screen family members
Explanation
Familial hypocalciuric hypercalcaemia (FHH) mimics mild primary hyperparathyroidism but needs no surgery. The discriminating test is the calcium to creatinine clearance ratio, which is below 0.01 in FHH and above 0.02 in primary hyperparathyroidism. Parathyroidectomy in FHH fails to cure the calcium because the defect is renal calcium sensing via CASR mutation, not gland pathology. Family screening confirms the autosomal dominant inheritance pattern.
Reference: Williams Textbook of Endocrinology, 14th ed.
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