Case Report: A case of mediastinal parathyroid adenoma leading to hypercalcemic crisis complicated by acute kidney injury and postoperative hungry bone syndrome.

A 61-year-old man was admitted to the hospital with fatigue and hypercalcemia, with serum calcium levels as high as 6.16 mmol/L and parathyroid hormone (PTH) levels >5000 pg/mL, accompanied by progressively rising serum creatinine levels (150→266 μmol/L). A neck ultrasound revealed a small nodule in the left parathyroid region, but 99mTc-MIBI imaging identified a focal area of increased radiotracer uptake within the mediastinum. Following multidisciplinary consultation, a thoracoscopic mediastinal mass resection was performed, and pathology confirmed an ectopic parathyroid adenoma (3.2 × 2.8 × 1.5 cm). Postoperatively, PTH levels dropped sharply to 56.17 pg/mL, accompanied by severe hypocalcemia (lowest 1.85 mmol/L) and numbness in the extremities, consistent with the presentation of hungry bone syndrome. Serum calcium levels gradually recovered following intravenous and oral administration of calcium supplements and calcitriol, and renal function also improved significantly. Although all components of this case have been reported individually, the combination of extreme biochemical values, acute kidney injury, and well-documented postoperative course is unusual and instructive. Functional imaging was decisive for localization; postoperatively, hungry bone syndrome should be anticipated and managed proactively. This case demonstrates the full clinical trajectory and offers practical lessons for similar complex presentations.