Patient information: Hypothyroidism (underactive thyroid) (The Basics)
Written by the doctors and editors at UpToDate

The thyroid is a butterfly-shaped gland in the middle of the neck. It sits just below the larynx (voice box). The thyroid makes two hormones, called T3 (triiodothyronine) and T4 (thyroxine), which control how the body uses and stores energy.

What is hypothyroidism?
— Hypothyroidism is a condition that makes you feel tired.
There is a gland in your neck called the thyroid gland. It makes thyroid hormone. This hormone controls how the body uses and stores energy (figure 1).
Hypothyroidism is the medical term for when a person does not make enough thyroid hormone. People sometimes confuse this condition with Hyperthyroidism, which is when a person makes too much thyroid hormone.

What are the symptoms of hypothyroidism?
— Some people with hypothyroidism have no symptoms. But most people feel tired. That can make the condition hard to diagnose, 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 and cause swelling (fluid buildup) in your ankles. Untreated hypothyroidism can also increase your blood pressure and raise your cholesterol—both of which increase the risk of heart trouble.
In women, hypothyroidism can disrupt monthly periods. It can also make it hard to get pregnant. In women who do get pregnant, hypothyroidism can cause problems. For instance, it can increase the chances of having a miscarriage and of having a baby with low intelligence.

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

How is hypothyroidism treated?
— Treatment for hypothyroidism involves taking thyroid hormone pills every day. After you take the pills for about 6 weeks, your doctor will test your blood to make sure the levels are where they should be. He or she might adjust your dose depending on the results. Most people with hypothyroidism need to be on thyroid pills for the rest of their life.
Thyroid hormone pills come in different brand name and generic forms. All the pills work equally well. But you should not switch from one generic or brand name to another. Switching between pills can cause your levels to go up and down.
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 women with hypothyroidism have healthy pregnancies. But your doctor will need to change your dose of thyroid hormone once you are pregnant. He or she will also need to measure your blood levels of thyroid hormone every 4 weeks. Pregnant women need changing doses of the hormone.

All topics are updated as new evidence becomes available and our peer review process is complete.
This topic retrieved from UpToDate on: Jun 14, 2016.

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