Hypothyroidism can be easily treated using thyroid hormone medicine. The most effective and reliable thyroid replacement hormone is man-made (synthetic). After starting treatment, you will have regular visits with your doctor to make sure you have the right dose of medicine.

In most cases, symptoms of hypothyroidism start to improve within the first week after you start treatment. All symptoms usually disappear within a few months. Infants and children with hypothyroidism should always be treated. Older adults and people who are in poor health may take longer to respond to the medicine.

• If you have had radiation therapy and have hypothyroidism, or if your thyroid gland has been removed, you will most likely need treatment for the rest of your life. If your hypothyroidism is caused by Hashimoto's thyroiditis, you might also need treatment for the rest of your life. Occasionally, thyroid gland function returns on its own in Hashimoto's thyroiditis.
• If a serious illness or infection triggered your hypothyroidism, your thyroid function most likely will return to normal when you recover.
• Some medicines may cause hypothyroidism. Your thyroid function will return to normal when you stop the medicines.
• If you have mild (subclinical) hypothyroidism, you may not need treatment but should be watched for signs of hypothyroidism getting worse. You and your doctor will talk about the pros and cons of taking medicine to treat your mild hypothyroidism. The dose of thyroid medicine must be watched carefully in people who also have heart disease because too much medicine increases the risk of chest pain (angina) and irregular heartbeats (atrial fibrillation).

Initial treatment

Your doctor will treat your hypothyroidism with the thyroid medicine levothyroxine (for example, Synthroid, Levoxyl, or Levothroid). Take your medicine as directed. You will have another blood test 6 to 8 weeks later to make sure the dose is right for you.

If you take too little medicine, you may have symptoms of hypothyroidism, such as constipation, feeling cold or sluggish, and gaining weight. Too much medicine can cause nervousness, problems sleeping, and shaking (tremors). If you have heart disease, too much medicine can cause irregular heartbeats and chest pain. People who also have heart disease often start on a low dose of levothyroxine, which is increased gradually.

If you have severe hypothyroidism by the time you are diagnosed, you will need immediate treatment. Severe, untreated hypothyroidism can cause myxedema coma, a rare, life-threatening condition.

Treatment during pregnancy is especially important because hypothyroidism can harm the developing fetus.

• If you develop hypothyroidism during pregnancy, treatment should be started immediately. If you have hypothyroidism before you become pregnant, your thyroid hormone levels need to be checked to make sure that you have the right dose of thyroid medicine. During pregnancy, your dose of medicine may need to be increased by 25% to 50%.²
• If you develop hypothyroidism after pregnancy (postpartum hypothyroidism), you also may need treatment. You will be retested for hypothyroidism if you become pregnant again. In some cases hypothyroidism will go away on its own; in other cases it is permanent and requires lifelong treatment.

Ongoing treatment