What Causes an Overactive Thyroid?
An overactive thyroid, a condition known as hyperthyroidism, occurs when the thyroid gland located in the neck produces too much of the hormones thyroxine (T4) and triiodothyronine (T3). Hyperthyroidism can be an acute (short-term) or chronic (long-term) condition resulting in symptoms such as difficulty concentrating, fatigue, frequent bowel movement, increased appetite, sweating, restlessness and change in weight. There are several different diseases or conditions that cause an overactive thyroid, which occurs in approximately 1 percent of the United States population, according to the National Endocrine and Metabolic Diseases Information Service.
