A 40-year-old woman who received a live-related renal transplant four years ago now has serum calcium 12.2 mg/dL, phosphorus 2.2 mg/dL, and intact PTH 320 pg/mL persisting beyond one year with normal graft function. Which statement best characterises her condition?
- A Tertiary hyperparathyroidism due to autonomously functioning parathyroid tissue, usually requiring parathyroidectomy ✓
- B Secondary hyperparathyroidism driven by declining graft function
- C Parathyroid carcinoma arising after chronic stimulation
- D Humoral hypercalcaemia of malignancy, since PTH assays cross-react with PTHrP
Correct answer: A. Tertiary hyperparathyroidism due to autonomously functioning parathyroid tissue, usually requiring parathyroidectomy
Explanation
Tertiary hyperparathyroidism is defined as persistent hypercalcaemia with elevated PTH after correction of the original stimulus, classically following successful renal transplantation. Glands that hyperplased during years of uraemic stimulation become autonomous and fail to suppress with restored mineral metabolism. Persistent elevation beyond one year with good graft function mandates subtotal or total parathyroidectomy with autotransplantation. Modern two-site immunoassays do not cross-react with PTHrP, excluding option D.
Reference: Schwartz's Principles of Surgery, 11th ed.
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