In healthy people, the thyroid makes just the right amounts of two hormones, T4 and T3, which have important actions throughout the body. These hormones regulate many aspects of our metabolism - affecting how many calories we burn, how warm we feel, and how much we weigh. They also have specific actions in most organs, such as the heart, which beats faster and harder under the influence of thyroid hormones. Hyperthyroidism is a condition caused by the effects of too much thyroid hormone on tissues of the body.
Patients usually experience fatigue, but have trouble sleeping.
Trembling of the hands and hard or irregular heart beat, called palpitations, may develop. They may become irritable and easily upset. When hyperthyroidism is severe, patients can suffer shortness of breath, chest pain, and muscle weakness. Other rare symptoms of this condition are vomiting, itching, heart failure, stroke, or even mental illness. Often symptoms of hyperthyroidism are gradual in onset and continue for weeks or months before patients fully realize that they are sick.