SUN-778 - Unexplained Persistent Mild Hypercalcemia in an Asymptomatic Patient with Incidental Electrocardiographic Abnormalities

Background
Hypercalcemia is commonly encountered in clinical practice, most often due to primary hyperparathyroidism or malignancy. However, persistent mild hypercalcemia with normal parathyroid hormone (PTH) levels and unrevealing diagnostic evaluation presents a clinical challenge. 

Clinical Case
A 42-year-old male of African descent with hyperlipidemia presented to the endocrinology clinic following an incidental finding of hypercalcemia (11.34 mg/dL) on pre-employment blood tests and electrocardiogram (ECG) showed ST-segment elevations in anterior precordial leads T-wave inversions in inferior limb and lateral precordial leads. Although, asymptomatic, he was sent to the emergency department (ED) for further evaluation. Vital signs were within normal limits. Laboratory testing: total serum calcium=11.75 mg/dL (nl 8.70-10.40). The following day calcium=10.47 mg/dL., TSH= 0.996 MIU/mL (normal 0.55-4.780). Chest x-ray was unremarkable. Cardiac tests=negative serial troponins; transthoracic echocardiogram-normal left ventricular ejection fraction with mild concentric left ventricular hypertrophy and no regional wall motion abnormalities; CT coronary angiogram-anomalous coronary artery with prominent artifact involving the left circumflex artery, but no obstructive coronary disease. One month later, in endocrinology clinic, he continued to deny symptoms of hypercalcemia (fatigue, polyuria, polydipsia, nephrolithiasis, bone pain, constipation, neurocognitive symptoms, chest pain, and dyspnea). The patient reported excellent exercise tolerance and routinely ran 1.5 miles without limitations. He took no medications and only used occasional alcohol, but no tobacco or recreational drug use. Family history: diabetes mellitus in father. Physical exam remained unremarkable. Lab: Total calcium=10.95 mg/dL, ionized calcium= 1.46 mmol/L (n1.16-1.32), urine calcium=15.8 mg (normal), 25-hydroxyvitamin D= 27.6 ng/mL (30.0-100.0), intact PTH=60.4 pg/mL (normal 18.4 -80.1), PTH-related peptide=11 pg/mL (nl=11-20), Angiotensin-converting enzyme (ACE)=elevated at 69 U/L (nl 9-67), Antinuclear antibody=negative, Gamma globulin=1.5 g/dL. Thyroid ultrasound showed a normal thyroid and no parathyroid adenoma. Repeat total and ionized calcium, 25-hydroxyvitamin D and intact PTH levels were all normal. Oral 25 Mg ergocalciferol daily was started. The patient was then lost to follow-up.  

Conclusion:
This case demonstrates that hypercalcemia may often present incidentallymwith unclear and various etiologies, and also present with various EKG abnormalities (QT, ST and t wave changes, prolonged PR, QRS, and others) in the absence of cardiac symptoms and unclear significance.

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