What is hypothyroidism?

Hypothyroidism means that the thyroid gland does not make enough thyroid hormone. Low levels of this hormone can cause many body functions to slow down.

Not growing normally is the most common sign. It can also cause your child to feel sluggish, gain weight, have a poor memory, or have a hard time focusing. The symptoms can be similar to depression.

Hashimoto's thyroiditis is the most common cause in children. In this condition, the body's immune system attacks the thyroid gland.

Your child needs to take thyroid hormone medicine every day. He or she should have a blood test at least once a year. This checks to be sure the medicine dose is right. Your child will keep taking medicine to replace the hormone that the thyroid gland doesn't make.

Hypothyroidism can be a serious disease. But children usually do well after starting treatment.

Although rare, hypothyroidism can occur in infants and children. If hypothyroidism is treated within the first month of life, a child will grow and develop normally. Untreated hypothyroidism in infants can cause brain damage, leading to intellectual disability and developmental delays. In the United States, all children are tested for hypothyroidism at birth.

Intellectual disability usually does not occur if hypothyroidism develops after age 3. But untreated childhood hypothyroidism typically delays physical growth and sexual development, including the onset of puberty. Children may gain weight yet have a slowed growth rate.

If you have low thyroid levels, you may feel tired, weak, or depressed. Other symptoms include dry skin, brittle nails, not being able to stand the cold, constipation, memory problems, and heavy or irregular menstrual periods. Symptoms occur slowly over time. You might not notice them or might mistake them for normal aging.

Your doctor will treat your low thyroid level with the thyroid pills levothyroxine. Most people start to feel better in a week or two. Your symptoms will probably go away within a few months. But you will likely need to keep taking the pills from now on.

It's important to take your medicine just the way your doctor tells you to. You will also need to see your doctor for follow-up visits to make sure you have the right dose. If you have mild hypothyroidism, you may not need treatment now. But you'll want to watch for signs that it's getting worse. If you have severe hypothyroidism by the time you are diagnosed, you will need treatment right away.

If you get hypothyroidism during pregnancy, treatment should be started right away. Low thyroid levels can harm the developing baby.

Thyroid hormones help regulate the way the body uses energy. You need thyroid hormone replacement when you do not have enough thyroid hormones in your blood (hypothyroidism). Depending on the cause of your hypothyroidism, you may need to take thyroid hormones for the rest of your life.

Thyroid hormones are usually taken by mouth. How much you need depends on your age, your body weight, and whether you are pregnant.

Thyroid hormone replacement is the only way to treat hypothyroidism. For most people, taking a thyroid hormone medicine:

• Reduces or stops the symptoms of hypothyroidism.
• Allows them to live normal lives.
• Reduces the risk of complications from having too little thyroid hormone in the blood, including a high level of fats and cholesterol in the blood.

People who take thyroid hormones need to have their blood checked regularly to make sure that they are taking the correct dose of replacement hormone. Children, pregnant women, and older adults may need to have their blood levels checked more often than other people.

Most cases of hypothyroidism in the United States are caused by Hashimoto's thyroiditis, which cannot be prevented.

Although you can't prevent hypothyroidism, you can watch for signs of the disease so it can be treated promptly. Some people who are at high risk for having hypothyroidism but do not have symptoms can be tested to see whether they have mild, or subclinical, hypothyroidism.

To diagnose hypothyroidism, your doctor will first ask you about your past health problems and do a physical exam. If your doctor thinks you have the condition, a simple blood test can show if your thyroid hormone level is too low.

Thyroid hormone medicine is the only way to treat hypothyroidism. Your doctor will treat your low thyroid level with the thyroid pills levothyroxine. Usually, thyroid hormone medicine:

• Reduces or gets rid of symptoms of hypothyroidism. Symptoms often improve within the first week after you begin therapy. All symptoms often go away within a few months.
• May reduce the risk of slowed physical growth, intellectual disability, and problems with behavior in infants and children.

After you start treatment, you'll have regular visits with your doctor to see if you have the right dose of medicine. Getting too much or too little thyroid hormone can cause problems.

Thyroid hormone medicine does not cause side effects if you take the correct dose. Depending on its cause, people who have hypothyroidism may need treatment for the rest of their lives.

Be sure to take your thyroid hormone medicine exactly as prescribed, and call your doctor if you think you are having a problem with your medicine. Tell your doctor about all prescription, herbal, or over-the-counter products you take. Try to eat a healthy diet, get enough sleep, and get regular exercise.

Many things may increase your risk for hypothyroidism. These include:

Age and being female.

Older adults are more likely to develop hypothyroidism than younger people. And women are more likely than men to develop thyroid disease.

Family history.

Hypothyroidism tends to run in families.

Previous thyroid problems.

Thyroid disease, an enlarged thyroid (goiter), and surgery or radiation therapy to treat thyroid problems increase the likelihood of having hypothyroidism in the future.

Some lifelong conditions.

Type 1 diabetes, vitiligo (an autoimmune disease that causes patches of light skin), pernicious anemia, and leukotrichia (premature gray hair) are seen more often in people who have hypothyroidism.

Iodine deficiency.

This is rare in the United States but common in areas where iodine is not added to salt, food, and water.

Medicines.

Some medicines can interfere with normal thyroid function, particularly lithium or amiodarone.

In the United States, the most common cause is Hashimoto's thyroiditis.

Worldwide, iodine deficiency is the number one cause of low thyroid levels.

Other common causes include:

• Thyroid surgery.
• Radioactive iodine therapy.
• External beam radiation. This is used to treat some cancers, such as Hodgkin lymphoma.

Less common causes

Less common causes include:

• Infections.
• Some medicines, such as lithium.
• Disorders of the pituitary gland or the hypothalamus.
• Consuming too much iodine.
• Being born with a thyroid gland that doesn't work right. (This is called congenital hypothyroidism.)

Hypothyroidism means that the thyroid gland doesn't make enough thyroid hormone. This hormone controls the way your body uses energy. Having a low level of thyroid hormone affects your whole body. It can make you feel tired and weak.

Expert groups differ in their recommendations for screening for hypothyroidism. For example:

• The American Thyroid Association and the American Association of Clinical Endocrinologists recommend that testing be considered for those older than age 60.
• The U.S. Preventive Services Task Force makes no recommendation for or against screening for people who do not have symptoms of thyroid problems. The USPSTF states that there is not enough evidence to support screening.

Talk to your doctor about whether testing is right for you.