Endocrine Abstracts

Background: Hungry bone syndrome is a relatively uncommon but serious complication in patients who underwent parathyroidectomy for primary hyperparathyroidism. The syndrome is described as a hypocalcaemia (corrected serum calcium<2.1 mmol/L) lasting longer than four days after parathyroidectomy in the presence of a normal or elevated parathyroid hormone (PTH). Treatment is challenging and guidelines are based on clinical experience. To restore calcium levels high doses of calcium and active vitamin D are needed.

Case Report: A 39-year-old woman with a medical history of kidney stones and osteoporosis was diagnosed with primary hyperparathyroidism. Corrected serum calcium was 2.72 mmol/L (2.15-2.50) in the presence of an elevated PTH (748 ng/L, 15-65). Further blood results showed a normal kidney function, a decreased phosphatase (0.51 mmol/L, 0.81-1.45), an elevated alkaline phosphatase (276 U/L, 38-126) and a decreased level of 25-hydroxyvitamin D (18.2 ng/mL, 30-100) for which substitution with D-cure was started. Guided by the results of localization studies a selective parathyroidectomy of the left (1.3 x 0.7 cm) end right (1.8 x 1.0 cm) inferior parathyroid adenoma was performed together with a total thyroidectomy because of bilateral thyroid nodules. Peri-operatively PTH normalized to a level of 57 ng/mL (18.5-88). Postoperatively, 1.6 g elemental calcium supplementation (calcium carbonate 4 g) per day was started. Histology revealed both thyroid nodules and parathyroid adenoma were benign. At discharge, the patient had a low normal corrected calcium levels (2.13 mmol/L, 2.18-2.60) with a normal PTH level (72 ng/L). One and a half month postoperatively, she complained of paraesthesia and muscle cramps. Blood sample revealed a low corrected serum calcium of 1.61 mmol/L in combination with an unexpected elevated PTH of 210 ng/L. Other electrolytes (potassium, phosphate, magnesium) and thyroid function were normal. Calciuria was low (0.73 mmol/24h, 2.50–8.00). Patient was admitted to intensive care for close monitoring. She required 7.2 g elemental calcium (6 g calcium gluconate intravenous, 12 g calcium carbonate peroral) and 4 μg active vitamin D to correct hypocalcaemia and correct symptoms of tetany. After 6 days, intravenous calcium was stopped and the patient was further treated with an oral calcium supplement. To maintain low normal calcium levels a total daily dose of 9.6 g elemental calcium (24 g calcium carbonate) along with 4 μg active vitamin D was required. Serum calcium concentration levels finally normalized after 2 weeks of admission and the patient was discharged. Six months postoperative, the dose of elemental calcium is reduced to 1.4 g (calcium carbonate 3.5 g) and active vitamin D to 3 μg to maintain a low normal corrected calcium level (2.15 mmol/L). PTH is still elevated (170 ng/L) and alkaline phosphatase is normalized (98 U/L).

Conclusion: We present a case of a severe hypocalcaemia due to a hungry bone syndrome after parathyroidectomy for primary hyperparathyroidism. Possible preoperative risk factors for the development of a hungry bone syndrome were the more than two-fold increased levels of PTH, increased alkaline phosphatase, depleted vitamin D status and osteoporosis (1). In this case report, the total daily dose of 9.2 g elemental calcium is within the range of 6-12 g to normalize calcium levels in HBS (1). Five months postoperative, the patient still requires calcium and active vitamin D supplements. There are no data about the mean duration of hungry bone syndrome, but can last up to 12 months postoperatively. To decrease the risk of a hungry bone syndrome in a hyperparathyroid patient with bone disease the use of preoperative bisphosphonates is suggested but there is a lack of high quality randomized studies (2).

References: 1. Witteveen JE, van Thiel S, Romijn JA, Hamdy NA. Hungry bone syndrome: still a challenge in the post-operative management of primary hyperparathyroidism: a systematic review of the literature. Eur J Endocrinol. 2013;168(3):R45–53.

2. Jakubauskas M, Beisa V, Strupas K. Risk factors of developing the hungry bone syndrome after parathyroidectomy for primary hyperparathyroidism. Acta Med Litu. 2018;25(1):45–51.