Detecting Primary Hyperparathyroidism with Image Discordant Findings

ABSTRACT

Introduction: Primary hyperparathyroidism is a common cause of hypercalcemia, with 80-85% of cases being due to a single gland adenoma. The sensitivity of imaging modalities varies, with ultrasound at 76%, sestamibi scintigraphy at 63%, and 4-dimensional computed tomography (CT) scan at 89%. Clinical Case A 48-year-old woman with a remote history of iron deficiency anemia presented with 2 weeks of dry cough. She reported associated body aches and fatigue, but review of systems was otherwise negative. Family history was notable for a maternal grandmother with an unknown thyroid disease. On presentation, her blood pressure was 115/74 mm Hg, temperature was 37.1 Celsius, pulse was 64 beats per minute, with a respiratory rate of 16 breaths per minute, and oxygen saturation of 100 percent on room air. On exam, there was no thyromegaly, and there were decreased breath sounds. Initial labs were notable for calcium of 11.4 mg/dL (reference range 8.4-10.2 mg/dL). Her rapid Covid antigen test was negative. A chest x-ray showed bilateral opacifications, suggestive of community acquired pneumonia. She was started on isotonic intravenous (IV) fluids, as well as ceftriaxone and azithromycin. The calcium remained persistently elevated and peaked at 12.6 mg/dL. Creatinine levels remained between 0.7-1. 0 mg/dL (reference range 0.5-1. 0 mg/dL). Phosphorus level was 3.6 mg/dL (reference range 2.5-4.5 mg/dL). Parathyroid hormone level was 174.6 pg/mL (reference range 37.87-83.87 pg/mL). 24-hour urinary calcium was 660 mg (reference range 0-320 mg). Ultrasound of the neck showed multiple mildly suspicious thyroid nodules, but no notable findings for the parathyroid gland. Subsequent nuclear medicine sestamibi scan revealed no discrete parathyroid adenomas. The 4-dimensional CT scan did not mention parathyroid pathology on the report. However upon review by a head and neck surgeon, a suspicious lesion was identified adjacent to the right thyroid lobe. Intervention was indicated given her age (<50), serum calcium > 1 mg/dL above the upper limit of normal, and 24-hour urinary calcium > 400 mg. The patient underwent a right neck exploration, and a right superior parathyroidectomy was performed. Conclusion: The patient met the criteria for primary hyperparathyroidism based on her normal kidney function, elevated serum calcium, and elevated parathyroid hormone. While imaging is frequently ordered, it is important to note that it does not have a role in confirming or ruling out the diagnosis of primary hyperparathyroidism. It should instead be used to localize abnormal parathyroid glands for operative planning. This case highlights the importance of surgical consultation in primary hyperparathyroidism, especially in the setting of negative or conflicting imaging results.Presentation No date and time listed