Treatment-resistant Hypercalcemia from Ectopic PTH Hypersecretion Suspected Secondary to Disseminated Ovarian Cancer

Hypercalcemia of malignancy (HCM) can present secondary to hypersecretion of parathyroid hormone (PTH)-related protein (PTHrP) from malignant tumors, but rare cases of HCM have also been documented due to inappropriate PTH secretion from ectopic neoplasms. Here, we report an unusual case of HCM due to hypersecretion of PTH suspected secondary to a disseminated mucinous ovarian adenocarcinoma. A 45-year-old female presented with severe hypercalcemia and significant elevations in both PTH and PTHrP two weeks after total abdominal hysterectomy with bilateral salpingo-oophorectomy and suboptimal debulking of a newly discovered left ovarian mucinous adenocarcinoma with numerous metastases. Ectopic PTH secretion was highly suspected after a negative parathyroid ultrasound. Pamidronate, calcitonin, and fluid resuscitation were unable to normalize her serum calcium, resulting in the need for dialysis and subsequent continuous renal replacement therapy. Further intervention with denosumab, etelcalcetide, and cinacalcet was attempted. Serum calcium began to decline, but repeat PTH resulted greater than 2,500 pg/mL. Unfortunately, the patient died just one week into her hospital course from septic shock and multi-organ system failure. While patients with localized PTH-secreting tumors carry a good prognosis, disseminated malignancies can result in significant morbidity and mortality due to severe treatment-resistant hypercalcemia.