Hypercalcaemic Crisis Associated with Hyperthyroidism: A Rare and Challenging Presentation

A 51-year-old female with a history of multinodular goitre presented with vomiting, abdominal discomfort, and generalized tiredness. Investigations revealed hypercalcemia (ionized calcium 1.41 mmol/L), hypokalaemia, suppressed parathyroid hormone, and significantly elevated free thyroxine (> 7.77 ng/dL) with a suppressed thyroid-stimulating hormone level consistent with hyperthyroidism. Further, the workup confirmed Graves’ disease as the underlying aetiology. Hyperthyroidism is occasionally associated with mild to moderate hypercalcemia, but severe hypercalcemia or hypercalcaemic crisis is an extremely rare complication. Prompt recognition and treatment are crucial to prevent life-threatening complications. The patient was treated with intravenous fluids, a low-calcium diet, zoledronic acid, carbimazole, and a beta-blocker, leading to improvement in her condition. This case highlights a rare occurrence of hypercalcaemic crisis in a patient with thyrotoxicosis due to Graves’ disease. Hyperthyroidism-induced hypercalcemia requires prompt recognition and multidisciplinary management involving endocrinologists, internists, and critical care specialists to prevent potentially life-threatening complications. Healthcare providers should consider the hypercalcaemic crisis in the differential diagnosis of hypercalcemia in the context of hyperthyroidism.