Thyroid storm is a complicated, life-threatening form of thyrotoxicosis. The causes are multifactorial and elevated iodothyronine levels are only one of many components. Usually, the transition from thyrotoxicosis to thyroid storm is ignited by non-thyroidal triggers. This is a rare condition observed with an incidence between 0.8 and 1.4 cases per 100,000 inhabitants. Diagnosis relies primarily on clinical criteria. Multimodal therapy aims at disrupting positive feedback loops between elevated levels of free T3 or T4 and their effects on target tissues and organs. Timely diagnosis and therapy help to reduce mortality to below 35%.