Delayed onset hungry bone syndrome following parathyroidectomy in a patient taking high dose cinacalcet for primary hyperparathyroidism
NJ Smart & JDT Morgan
Parathyroidectomy remains the mainstay of treatment for primary hyperparathyroidism. Routine measurements of calcium and PTH mean that primary hyperparathyroidism is being detected and treated at an earlier stage. Consequently the profound hypocalcaemia pathognomonic of hungry bone syndrome, usually commencing within 48 hours of surgery, is now rarely seen in clinical practice.
We present a 66 year old female patient who had incidental hypercalcaemia detected when admitted for stroke rehabilitation. Despite infusions of pamidronate she remained hypercalcaemic and was commenced on cinacalcet and the dose titrated to 90 mg q.d.s. This controlled her hypercalcaemia and reduced her PTH by over 60%. Four months later a right lower parathyroid adenoma was surgically removed and confirmed histologically.
Postoperatively, PTH was within the normal range at 6 hours and calcium levels were mildly elevated for 2 days but normal by day 3. Between the 5th and 8th post op days she had mild symptomatic hypocalcaemia (2.042.15 mmol/l) treated with oral calcium and alfacalcidol. However on the 9th post op day she became profoundly hypocalcaemic (1.72 mmol/l) with a mildly raised alkaline phosphatase of 118 IU/l, diagnostic of hungry bone syndrome. In rat models of secondary hyperparathyroidism calcimimetics have improved bone strength by inducing a controlled hungry bone syndrome without hypocalcaemia. Similar results have been achieved in man. Conversely no such improvement in bone mineral density has been observed in patients with primary hyperparathyroidism treated with cinacalcet and some markers of bone turnover were actually increased. This is the first report of a patient with primary hyperparathyroidism being treated with cinacalcet subsequently having parathyroidectomy. Such patients may be at increased risk of developing hungry bone syndrome.
Recent advances in the medical management of primary hyperparathyroidism may have important implications for the perioperative management of this condition.