Parathyroid carcinoma presenting as hypercalcemic crisis with severe gastrointestinal manifestations: a case report

Parathyroid carcinoma is a rare endocrine malignancy that can present with severe hypercalcemia and nonspecific symptoms. An 18-year-old woman presented with persistent nausea and vomiting for more than 1 month, accompanied by fatigue and constipation. Laboratory examination revealed severe hypercalcemia, with a serum calcium level of 4.40 mmol/L and a markedly elevated parathyroid hormone (PTH) level of 532.6 pg/mL. Parathyroid ultrasonography revealed markedly hypoechoic nodules posterior to both thyroid lobes, suggesting a parathyroid origin. The patient underwent surgical resection of a left inferior parathyroid tumor. Histopathological examination demonstrated invasive growth of the parathyroid tumor, and the diagnosis of parathyroid carcinoma was established based on the histopathological and immunohistochemical findings. Following surgery, serum calcium and PTH levels decreased to 2.64 mmol/L and 65.1 pg/mL, respectively, accompanied by marked improvement in the patient's symptoms. At the 1-month follow-up, serum calcium and PTH levels had further normalized to 2.34 mmol/L and 33.06 pg/mL, respectively. This case highlights that persistent gastrointestinal symptoms, particularly nausea and vomiting, may be manifestations of severe hypercalcemia associated with parathyroid carcinoma. Careful assessment of serum calcium and PTH levels is therefore important in patients with unexplained gastrointestinal symptoms, especially when accompanied by other manifestations suggestive of hypercalcemia.