Approach to the patient with severe hyperthyroidism-related complications.

Hyperthyroidism is a prevalent endocrine disorder that can lead to severe multisystem complications, including atrial fibrillation (AF), thyrotoxic periodic paralysis (TPP), and thyroid storm (TS). This review discusses the pathophysiology, clinical presentation, and management challenges of these complications through illustrative clinical cases. AF is the most common cardiovascular manifestation, with restoration of euthyroidism and rate control being central to treatment. TPP presents with transient muscle weakness due to hypokalemia from intracellular potassium shift, requiring cautious potassium supplementation and hyperthyroidism control. TS is a life-threatening endocrine emergency characterized by multisystem decompensation, necessitating prompt multimodal therapy including antithyroid drugs, beta-blockers, corticosteroids, and supportive care. Thus, early recognition and tailored management remain the cornerstones of successful treatment for these severe complications of hyperthyroidism.