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Abstract: FR-PO686

Hypercalcemia Secondary to Malignancy-Associated Ectopic PTH Secretion: A Rare Mimicker of Primary Hyperparathyroidism

Session Information

Category: Trainee Case Report

  • 1500 Onco-Nephrology

Authors

  • Seay, Norman Winn, Duke University, Durham, North Carolina, United States
  • Ortiz Melo, David I., Duke University Medical Center, Durham, North Carolina, United States
  • Scialla, Julia J., Duke University, Durham, North Carolina, United States
Introduction

Hypercalcemia affects nearly 30% of patients with cancer, and malignancy-related hypercalcemia is the most common cause of hypercalcemia in hospitalized patients. In most cases, hypercalcemia is due to tumor secretion of PTHrP, osteolytic metastases or increased production of 1,25 (OH)2D. We present a very rare case of malignancy-related hypercalcemia due to ectopic production of intact PTH in a patient with hepatocellular carcinoma.

Case Description

A 61-year-old man with history of hepatocellular carcinoma and hepatitis C infection complicated by cryoglobulinemia and CKD stage 4 was admitted with complaints of malaise, abdominal pain, dyspepsia, constipation, and inability to ambulate after suffering a left femoral fracture. Labs upon admission were notable for ionized calcium 12.7 mg/dL (normal 8.5-10.1), PTH 397 pg/mL (normal 14-72), PTH-rp 16 pg/mL (normal 14-27), and 1,25OH-vitamin D 12 pg/mL (normal 18-72). Further hypercalcemia workup included a parathyroid ultrasound and Sestamibi scan that were negative for parathyroid adenoma or carcinoma. An abdominal ultrasound revealed known liver mass attributed to his HCC and a new left upper quadrant mass adjacent to the spleen. The para-splenic lesion was FDG-avid on PET/CT. CT-guided biopsy of the left upper quadrant mass was consistent with HCC and stained positive for parathormone, confirming the diagnosis of intact PTH-secreting HCC. He was not a surgical candidate. Hospital course was complicated by refractory hypercalcemia (serum Ca as high as 14 mg/dL) despite generous intravenous normal saline, calcitonin, furosemide, and high dose cinacalcet (90 mg BID). The patient responded to 60 mg pamidronate. His serum calcium at discharge was 10.7 mg/dL.

Discussion

This patient had hypercalcemia due to ectopic intact PTH secretion, which is exceedingly rare. Very few case reports have been described, mostly involving solid tumors, including neuroendocrine, ovarian, rhabdomyosarcoma, gastric, hepatocellular, kidney, lung, parotid, and breast cancers. Because of elevated PTH, hypercalcemia in this setting could be mistaken for primary hyperparathyroidism, which could lead to an unnecessary neck exploration as an attempt to identify a parathyroid adenoma. Hypercalcemia in the setting of elevated PTH and non-parathyroid malignancy should thus raise suspicion for this entity.