An overactive thyroid produces more thyroid hormones than the body needs, and the medical term for the condition is hyperthyroidism, according to WebMD. Women have a higher risk of developing the condition than men.
An enlarged thyroid, known as a goiter, is the most common symptom of hyperthyroidism. Other common symptoms of the condition include anxiety, frequent bowel movements, bulging eyes, muscle weakness and weight loss. A rapid heart beat and shaky hands can also point to hyperthyroidism, according to WebMD.
There are several causes of hyperthyroidism, including Graves' disease, thyroiditis, thyroid nodules, excess iodine and thyroid medications, according to WebMD. Graves' disease is an autoimmune disease that forces the body to make an antibody that affects the thyroid. Thyroiditis is an inflammation of the thyroid that can appear in postpartum women. Thyroid nodules are lumps that form on the thyroid. Certain medications and foods can cause the body's iodine levels to rise, and a patient who takes thyroid medication to treat hypothyroidism, which is an underactive thyroid, can develop hyperthyroidism by taking too much medication.
Hyperthyroidism can be treated with anti-thyroid medication, radioactive iodine and surgery. Patients who choose one of the last two options need to take a thyroid medication for the rest of their lives because these treatments cause hypothyroidism, according to WebMD.