SAT211 PTH-secreting Endometrial Carcinoma: A Rare Cause of Hypercalcemia

Disclosure: E. Fanous: None. P. Park: None. L. Rakhlin: None. Introduction: Hypercalcemia of malignancy (HCM) is a common occurrence in advanced cancer, but it is rare for gynecological malignancies to be the cause (1). Case Presentation: Our patient is a 48-year-old postmenopausal female with diabetes mellitus and obesity who presented with pelvic pain and vaginal spotting over the course of 2 months. She also reported unintentionally losing approximately 60 lbs over the past year. A CT scan of the pelvis revealed a 6.1 cm uterine mass and thickening of the endometrium up to 2.4 cm. Her electrolyte levels were normal at the time of presentation. A biopsy of the endometrium was performed, and the pathology report indicated endometrial carcinoma. The patient was scheduled for a total hysterectomy and bilateral salpingo-oophorectomy (TAH/BSO). A few weeks prior to her scheduled surgery, the patient reported increased thirst and urination, which she attributed to her diabetes and intake of an SGLT2 inhibitor. On the day of surgery, she was found to have a calcium level of 15.4 mg/dl and an albumin level of 3.6 g/dl. She denied taking calcium supplements or Vitamin D3. The workup for hypercalcemia revealed a PTH level of 338 pg/ml, an undetectable PTH-rp level, and normal levels of Vitamin D1,25 and Vitamin D25. Additional imaging showed numerous pulmonary nodules, which were later confirmed to be metastases from endometrial carcinoma. The thyroid gland and surrounding soft tissue were noted to be unremarkable on available CT images. The patient received a single dose of zolendronic acid and was started on cinacalcet 30 mg twice a day. The calcium gradually normalized. She was initiated on chemotherapy with paclitaxel and carboplatin and underwent a palliative TAH/BSO. Cinacalcet was discontinued after several cycles of chemotherapy. Two months later, the PTH level was checked and found to be 34 pg/ml, with a normal calcium level of 9.5 mg/dl and an albumin level of 4.1 g/dl. Given that the hypercalcemia resolved and the PTH level normalized after chemotherapy and hysterectomy, it is believed that the endometrial carcinoma was the source of ectopic PTH. Conclusion: Approximately 5% of gynecological malignancies are associated with paraneoplastic hypercalcemia [1]. We present a rare case of PTH-secreting endometrial carcinoma, in which surgery and chemotherapy resulted in complete resolution of hypercalcemia and normalization of PTH. Clinicians should consider ectopic PTH production as part of the differential diagnosis in patients who present with malignancy and hypercalcemia. References: 1. Savvari P, Peitsidis P, Alevizaki M, et al. Paraneoplastic humorally mediated hypercalcemia induced by parathyroid hormone-related protein in gynecologic malignancies: A systematic review. Onkologie. September. 2009;32:517-23. Presentation: Saturday, June 17, 2023