Hungry bone syndrome (HBS) is characterized by persistent hypocalcemia and hypophosphatemia as a result of extensive remineralization following parathyroidectomy. It is a known but uncommon complication of parathyroid surgery, seen in 13–30% of cases. In this article, we report the case of a 36-year-old woman with increased thirst and polyuria as the first manifestation of primary hyperparathyroidism caused by an ectopic parathyroid adenoma located in the anterior mediastinum. After a single-port Thoracoscopic parathyroidectomy, the patient presented clinical signs of hypocalcemia consistent with hungry bone syndrome. This report highlights the diagnostic approach, surgical management, and postoperative care, emphasizing the importance of early recognition and intervention.