Hyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The common symptoms of hyperthyroidism are: goiter (visibly enlarged thyroid gland) or thyroid nodules, difficulty concentrating, fatigue, frequent bowel movements, heat intolerance, increased appetite, increased sweating, nervousness, restlessness, irregular menstrual periods in women, and weight loss (rarely, weight gain). Among the most important signs of hyperthyroidism are: thyroid enlargement, tremor, hyperactive reflexes, or an increased heart rate. The elderly may complain predominantly of heart problems with a fast or irregular heart beat, breathlessness and ankle swelling, whereas children tend to hyperactivity, with a short attention span. Sometimes hyperthyroidism is diagnosed by abnormal blood levels of thyroid hormones, often in the absence of any symptoms. This disease may also affect the results of cholesterol, triglycerides and glucose test. Untreated, hyperthyroidism has many complications, some of which are severe and affect the quality of life.