Hyperthyroidism is an immune disorder caused by autoimmune dysfunction and is characterized by diffuse enlargement of thyroid cells and an increase in thyroid hormone levels. Hyperthyroidism can cause cardiac arrhythmias, such as atrial fibrillation, persistent hyperthyroidism, and a long history of the disease, which can lead to heart enlargement and heart failure. Hyperthyroidism can also lead to metastatic hypokalemia and muscle weakness. Hyperthyroidism can also lead to hyperthyroidism-associated ophthalmopathy, which is characterized by protrusion of the eyeballs, photophobia, lacrimation, diplopia, pain and, in severe cases, blindness. Persistent hyperthyroidism can lead to significant protein depletion and weight loss, followed by negative nitrogen balance and malnutrition, leading to other co-morbidities.