SAT-344 Venous Thromboembolism Caused by Primary Hyperparathyroidism

Background. Primary hyperparathyroidism (PHPT) is often overlooked as a potential etiology of hypercoagulability and thrombosis. We present a case in which PHPT was the only identifiable risk factor for an episode of venous thromboembolism (VTE). Case. A 64 year old female with no chronic health problems presented to the emergency department for evaluation of dyspnea and right lower extremity pain. Symptoms had steadily increased in severity over approximately one week. The patient denied any long distance travel, sustained immobility, or tobacco use, and she was not taking any prescription or over-the-counter medications. Examination was notable for right distal lower extremity pain to palpation, but no swelling or erythema was observed. Elevated D-dimer (4.00 mg/mL, < 0.50) and hypercalcemia (12.7 mg/dL, 8.8–10.5) were discovered on initial laboratory testing, and an ECG showed sinus tachycardia. CT angiography of the chest revealed extensive, bilateral pulmonary emboli, and lower extremity venous Doppler studies confirmed a right lower extremity deep venous thrombus (DVT). Unequivocally elevated intact parathyroid hormone (PTH) level (235 pg/mL, 12–88) confirmed a diagnosis of PHPT, and an apparent left lower parathyroid adenoma was identified by both Tc99m parathyroid scintigraphy and neck ultrasonography. After hydration, serum calcium remained in the range of 11.5–12.0 mg/dL. The patient was discharged home on the direct factor Xa inhibitor rivaroxaban (Xarelto™) with a plan for six months of anticoagulation before parathyroidectomy. Conclusions. The skeletal, neuromuscular, cardiovascular, and neuropsychiatric manifestations of PHPT are well described, but little is published regarding PHPT and VTE. In a multivariate analysis of participants in the fourth and fifth Tromsø surveys controlled for age, sex, and BMI, simultaneous elevations of PTH and serum calcium were associated with a nearly 80% increased risk of VTE. PHPT has been linked to several changes that predispose to a hypercoagulable state and thrombosis including dehydration, vasoconstriction, increased platelet count and levels of coagulation factors VII and X, elevated tissue plasminogen activator inhibitor-1 and D-dimer levels, and diminished tissue factor pathway inhibitor levels. Unfortunately, risk of VTE is not addressed in series documenting long-term outcomes for patients undergoing parathyroidectomy for management of PHPT. However, in cases of VTE where PHPT is diagnosed, parathyroidectomy should be considered to potentially improve hypercoagulability and reduce the risk of subsequent VTE.