Transient Primary Hyperparathyroidism Following Viral Illness in the Absence of Structural Parathyroid Abnormalities: A Case report

Primary hyperparathyroidism (PHPT) is typically a persistent disorder caused by a parathyroid adenoma requiring surgical intervention. Transient PHPT (tPHPT) refers to a rare phenomenon in which spontaneous normalization of hypercalcemia and PTH occurred without surgical or pharmacological intervention. The most common cause of tPHPT is spontaneous infarction or hemorrhage of adenoma. We report a unique case of tPHPT following upper respiratory infection (URI) in a patient without identifiable adenoma, suggesting a transient inflammatory 'parathyroiditis' mechanism. A 60-year-old woman was referred for evaluation of asymptomatic hypercalcemia (serum calcium 11.3–11.4 mg/dL) identified during preoperative testing for lingual tonsillectomy. Her ionized calcium was 5.9–6.1 mg/dL. She also developed inappropriately normal followed by elevated iPTH (57–110 pg/mL). The biochemical peak occurred after several episodes of URI . The patient had no history of renal disease or malignancy, and no use of thiazides, lithium, or vitamin D/calcium supplements. Laboratory evaluation, including creatinine, 25-hydroxyvitamin D, and CASR gene sequencing, was unremarkable. Neck ultrasound revealed multinodular goiter and mild hypervascularity but no parathyroid abnormalities. Without intervention, serum calcium, iPTH, and alkaline phosphatase spontaneously normalized (calcium 9.1–9.6 mg/dL, iPTH 37–38 pg/mL, ALP 105-117 IU/L) within 4, 8, and 11 months, respectively. Remission has persisted for over three years. Transient PHPT may occur via a post-viral, non-infarction mechanism. In PHPT patients with recent viral illness and no localized adenoma on imaging, a period of biochemical observation may be appropriate to prevent unnecessary surgery.