What is the Difference Between Hypothyroidism and Hyperthyroidism?

Hypothyroidism occurs when your thyroid produces too little hormone, while hyperthyroidism happens when it produces too much. Hypothyroidism affects about 5% of Americans and causes symptoms like fatigue, weight gain, cold intolerance, and slow heart rate. Hyperthyroidism affects 1.3% of the population and triggers opposite symptoms including rapid heartbeat, weight loss, heat intolerance, and anxiety. Both conditions are diagnosed with blood tests, usually including TSH and free T4. A T3 test may also be useful, especially when hyperthyroidism is suspected. Treatment for hypothyroidism involves daily hormone replacement therapy, while hyperthyroidism may require antithyroid medications, radioactive iodine, or surgery depending on the underlying cause.