Primary hyperparathyroidism is treated surgically. Postoperatively, close monitoring of blood calcium levels is necessary to detect any hypocalcemia. Postoperative PTH assays can be performed within 24hours to identify patients who will not develop permanent hypoparathyroidism. Hypocalcemia may be caused by hypoparathyroidism (especially in the case of multi-glandular surgery or revision surgery) or by hungry bone syndrome. The latter should be suspected in case of major skeletal damage or severe preoperative vitamin D deficiency. It leads to severe hypocalcemia with normal or elevated PTH concentration, hypophosphatemia, hypomagnesemia, and low calciuria despite high doses of calcium and 1–25 OH vitamin D. Treatment of postoperative hypocalcemia depends on severity, symptoms and surgical procedure. In uni-glandular surgery, symptomatic treatment with calcium alone is recommended (0.5 to 1g/day). In multi-glandular involvement or repeat surgery, treatment with calcium (1 to 3g/day) is recommended if hypocalcemia is symptomatic or profound (<1.9mmol/L) (i.e. 76mg/L). If it is insufficient, the potential contribution of active vitamin D treatment should be assessed with an endocrinologist. If hypocalcemia is treated, patients should preferably be monitored by an endocrinologist (blood calcium level, calciuria and possibly phosphatemia and PTH). Under medical treatment of hypoparathyroidism, blood calcium levels should be monitored at least every 3 months for the first year, then at least twice a year.