Primary hyperparathyroidism is a common endocrinopathy which is nowadays diagnosed incidentally. Calcium levels range from "normal" to extremely high which can be life-threatening. We report the case of a female patient who was admitted to hospital for unspecific symptoms ultimately referable to severe hypercalcemia secondary to a large parathyroid tumor. After an intensive medical treatment (hydration, diuretics, steroids, bisphosphonate) leading to reduction of calcium levels, the patient underwent surgery with exeresis of the parathyroid mass proved an adenoma and normalization of calcium levels; nevertheless a few days after discharge symptomatic hypocalcemia occurred and was successfully managed by means of calcium and vitamin D therapy which is still required three months after surgery.