Abstract
Graves' disease (GD) is an autoimmune thyroid disease, which is considered the most common cause of primary hyperthyroidism. GD usually manifests with symptoms such as tremors, palpitations, heat intolerance, weight loss, and specific signs on physical examination (proptosis and pretibial myxedema). However, systemic involvement is also recognized, for example, hepatic involvement in patients with GD may range from asymptomatic laboratory findings of liver function derangement (either transaminases elevations or intrahepatic cholestasis) up to hepatic failure. We describe a rare case of Graves’ thyrotoxicosis presenting with severe cholestasis and non-parathyroid hormone-related hypercalcemia. An extensive evaluation for hepatobiliary causes of cholestasis, including hepatic biopsy, was entirely negative. The patient was successfully treated with methimazole with subsequent clinical and biochemical improvement.