Lessons learned from the management of Hungry Bone Syndrome following the removal of an Atypical Parathyroid Adenoma

Hungry Bone Syndrome (HBS) refers to rapid, profound, and prolonged hypocalcemia associated with hypophosphatemia and hypomagnesemia occurring in patients with increased bone turnover after successful management of the underlying disorder. We describe a male patient with primary hyperparathyroidism (PHPT), in whom HBS was diagnosed 6 months after parathyroidectomy. Histopathologic examination revealed an atypical parathyroid adenoma (APA), while immunohistochemistry showed cell proliferation index Ki-67 10% and overexpression of cyclin D1 (>90%). Preoperative treatment with vitamin D3 had normalized 25OHD and alkaline phosphatase levels, reflected in an improvement in bone turnover prior to surgery. Postoperative treatment for HBS with alfacalcidol, calcium, vitamin D3 and magnesium was administered for a long period. This treatment prevented severe postoperative hypocalcemia and he was discharged two days later. Preoperative cinacalcet treatment did not reduce hypercalcemia implying that the tumor had lack of calcium-sensing receptors (CaSR). In conclusion, preoperative restoration of low 25OHD levels is essential for prevention of HBS. Postoperative treatment with active metabolites of vitamin D must be initiated as early as possible, in order to prevent or minimize the development of HBS, and to reduce the duration of hospitalization.