Humoral hypercalcemia of benignancy secondary to parathyroid hormone-related protein secreting uterine leiomyoma

A 48-year-old women admitted with polyuria and polydipsia. She was found to be hypercalcemic despite suppressed parathormone (iPTH) levels. Subsequently checked parathormone related-protein (PTHrP) level was 2.5 pmol/L (expected normal level <1.3 pmol/L). An extensive workup for a malignancy revealed no abnormality, except for an uterine leiomyoma, 7.1 cm in size. Total abdominal hysterectomy and salpingo-oophorectomy were performed. After the surgical removal of uterine leiomyoma, serum calcium (9.3 mg/dL), iPTH (29.4 pg/mL), and PTHrP (<1.3 pmol/L) levels were normalized. The diagnosis of humoral hypercalcemia of benignancy secondary to PTHrP was confirmed. One month later, her calcium and iPTH levels were normal and 1 year later still remain within the normal ranges. Our case indicates that PTHrP associated hypercalcemia does not solely result from a malignant tumor. Benign tumors like uterine leiomyoma might also cause humoral hypercalcemia.