Patient education: Hypothyroidism (underactive thyroid) (The Basics)

What is hypothyroidism? — Hypothyroidism happens when a gland in your neck, called the thyroid gland, makes too little thyroid hormone. This hormone controls how the body uses and stores energy (figure 1).

With a different condition, hyperthyroidism, the thyroid gland makes too much thyroid hormone. With hypothyroidism, it does not make enough. Doctors sometimes also use the term "underactive thyroid."

What are the symptoms of hypothyroidism? — Some people with hypothyroidism have no symptoms. But most people feel tired. That can make it hard to know if a person has it, because a lot of conditions can make you tired.

Other symptoms of hypothyroidism include:

●Lack of energy

●Getting cold easily

●Developing coarse or thin hair

●Getting constipated (having too few bowel movements)

If it is not treated, hypothyroidism can also weaken and slow your heart. This can make you feel out of breath or tired when you exercise. It can also cause swelling (fluid buildup) in your ankles. Untreated hypothyroidism can also increase your blood pressure and raise your cholesterol. Both of these things increase the risk of heart problems.

Hypothyroidism can disrupt monthly periods. It can also make it hard to get pregnant. In people who do get pregnant, hypothyroidism can cause problems. For instance, it can increase the chances of having a miscarriage. (A miscarriage is when a pregnancy ends on its own before 20 weeks.)

Is there a test for hypothyroidism? — Yes. Your doctor or nurse can check for hypothyroidism using a simple blood test.

How is hypothyroidism treated? — Treatment involves taking thyroid hormone pills every day. After you take the pills for about 6 weeks, your doctor or nurse will test your blood again. This is to make sure the levels are where they should be. They might adjust your dose depending on the results. Most people with hypothyroidism need to keep taking thyroid pills for the rest of their life. This gives your body the right level of the hormone it cannot make on its own.

Thyroid hormone pills come in different brand name and generic forms. All the pills work equally well. If possible, you should try to stick with the same generic or brand name. But switching between pills does not cause problems for most people. Talk to your doctor or nurse if you want to switch for some reason.

Never change your dose of thyroid hormone on your own. Taking too much thyroid hormone can cause heart rhythm problems and even damage your bones.

What if I want to get pregnant? — You can try to get pregnant. Many people with hypothyroidism have healthy pregnancies. But your doctor or nurse will most likely need to change your dose of thyroid hormone once you are pregnant. That's because you need more thyroid hormone during pregnancy. They will also measure your levels of thyroid hormone 4 weeks after any change in your dose, and at least once during each trimester of pregnancy.

More on this topic

Patient education: Hyperthyroidism (overactive thyroid) (The Basics)
Patient education: Hyperthyroidism (overactive thyroid) and pregnancy (The Basics)
Patient education: Thyroiditis after pregnancy (The Basics)

Patient education: Hypothyroidism (underactive thyroid) (Beyond the Basics)