Ectopic Production of Parathyroid Hormone and Production of Parathyroid Hormone-related Protein in Dedifferentiated Endometrial Carcinoma Induced Severe Hypercalcemia

Hypercalcemia is a significant complication in cancer patients, primarily caused by parathyroid hormone-related peptide (PTHrP) and, rarely, by parathyroid hormone (PTH) production from tumors. We report a case of severe hypercalcemia in a woman with uterine cancer who exhibited elevated PTH and PTHrP levels. Surgical intervention revealed dedifferentiated endometrial carcinoma. Postoperatively, PTH and PTHrP levels normalized but subsequently increased due to metastases. A molecular analysis confirmed the expression of the PTH gene and protein within the tumor, indicating ectopic PTH production. In diagnosing and treating cancers, it is necessary to consider not only PTHrP production but also ectopic PTH production.