Concurrent Primary Hyperparathyroidism and Humoral Hypercalcemia of Malignancy in a Patient with Clear Cell Endometrial Cancer

A 65-year-old Caucasian woman with a known history of clear cell endometrial cancer presented with hypercalcemia. Further evaluation demonstrated that the patient had primary hyperparathyroidism due to a parathyroid adenoma, as well as an increased parathyroid hormone-related peptide secondary to her malignancy. To the best of our knowledge, this is the first reported case of a female patient with concurrent primary hyperparathyroidism and humoral hypercalcemia of malignancy. This case illustrates the importance of considering a broad differential when evaluating patients with hypercalcemia. It also emphasizes the importance of recognizing the biochemical interplay between parathyroid hormone and parathyroid hormone-related peptide.