MON-776 - Hypercalcemia as A Result of Uterine Leiomyomas: A Case Report

Humoral hypercalcemia is commonly associated with malignancy and rarely reported in benign conditions. We present a rare case of hypercalcemia secondary to parathyroid hormone–related protein (PTH-rP) secretion from uterine leiomyomatosis.

A 40-year-old woman presented to the emergency room with acute abdominal pain and menorrhagia. Initial labs revealed hypercalcemia with calcium of 11.2 mg/dL (8.2-10.2 mg/dL) and ionized calcium of 1.40 mmol/L (1.00-1.35 mmol/L). CT scan of her abdomen showed an enlarged uterus with multiple masses, lymphadenopathy, pulmonary nodules, a sclerotic bone lesion, and a tumor thrombus in the right gonadal vein extending into the inferior vena cava. A subsequent PET scan demonstrated nonmetabolic pulmonary and bone lesions raising concern for leiomyomatosis with possible metastases. Further laboratory evaluation revealed a suppressed parathyroid hormone (PTH) of 9 pg/mL (15-65 pg/mL), an elevated parathyroid hormone related protein (PTH-rP) of 45 pg/mL (11-20 pg/mL), low 25-Hydroxy Vitamin D of < 7 ng/mL (>20 ng/mL), and normal 1,25-Hydroxy Vitamin D.

The patient was initially treated with intravenous hydration for hypercalcemia. Medical management of her leiomyomatosis was refractory to treatment with letrozole, leuprolide, and indomethacin. She subsequently underwent an exploratory laparotomy and total abdominal hysterectomy. Pathology confirmed the diagnosis of leiomyomatosis. Postoperatively, serum calcium, ionized calcium, PTH, and PTH-rP levels normalized. These findings supported the conclusion that the uterine leiomyomata were the source of PTH-rP and the cause of hypercalcemia. The nature of the pulmonary and bone lesions remains uncertain.

Humoral hypercalcemia is usually associated with malignancy, though rare benign etiologies exist. Leiomyomatosis is an uncommon cause of PTH-rP mediated hypercalcemia. This case emphasizes that benign gynecological conditions should be considered in the differential diagnosis of hypercalcemia in the absence of an identifiable malignancy.

In conclusion, Leiomyomatosis is a rare cause of PTH-rP mediated hypercalcemia and can resolve entirely following surgical resection.

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