Thyroid Testing

What is Thyroid Testing?

While there are a number of Thyroid tests available, each one of them is used to determine how well the thyroid gland is operating in a patient. The thyroid gland is a butterfly-shaped gland positioned in front of an individual’s trachea (windpipe) and below the larynx (voice box) which makes hormones used by the body to regulate how it uses energy. The gland utilizes iodine taken from food to produce two hormones: T4 (thyroxine) and T3 (triiodothyronine), and stores these hormones for release into the body as needed. These hormones play a tremendous role in the development of the brain from birth to 3 years of age, and also help a person grow and develop normally through their childhood. They also contribute to health in adults by regulating the way a person’s body uses energy, where over- and underproduction of the hormone can cause serious health issues in an individual.

Who May Need a Thyroid Test?

Thyroid tests can be performed on men and women; however, women are often the most susceptible to health issues relating to thyroid dysfunction. A Thyroid test is designed to find out whether or not a thyroid gland is working properly, as an underactive thyroid gland can cause hypothyroidism, while an overactive thyroid gland can cause hyperthyroidism.

Hypothyroidism’s symptoms include weight gain, fatigue, dry skin, constipation, frequent menstrual periods in women, and a feeling of being too cold. Hyperthyroidism’s symptoms include weight loss, rapid heart rate, diarrhea, irregular or absent menstrual periods in women, and a feeling of being too hot. For those already receiving, or having received, various treatments for thyroid issues, a Thyroid test is also utilized to determine how well the treatment is working. Newborns also receive Thyroid tests to determine if their thyroid function is normal in order to avoid growth and developmental issues which may result from abnormal levels of the hormone.

What Should I Expect from My Thyroid Test?

Thyroid tests begin with a blood sample being drawn from a patient in order for it to be analyzed by a lab. Though ranges can vary from lab to lab, most physicians use a common reference range when referring to the results of a Thyroid test. After receiving your results, speak with your doctor about where your thyroid levels are located in this range. Sometimes levels that appear to be outside those considered normal fall within the normal range for you as an individual and the lab which prepared the results. For more detailed information on your thyroid, hypothyroidism, and hyperthyroidism, read the information below.

What is Hyperthyroidism?

Hyperthyroidism is overactivity of the thyroid gland. This means the gland makes too much thyroid hormone. Too much hormone speeds up chemical reactions in the body. This causes mental and physical changes.
The thyroid gland is a small gland at the lower front of the neck. This gland takes iodine from the food you eat to make hormones called thyroxine (T4) and triiodothyronine (T3). The hormones control your metabolism (the process of turning the food you eat into energy). The thyroid gland is critical for maintaining body temperature and controlling heart rate, appetite, and digestive tract function.
The most common form of hyperthyroidism is called Graves' disease. It occurs more in women than men, especially women in the childbearing years between 20 and 40.

How Does Hyperthyroidism Occur?

Possible causes are:

• Your immune system is not working properly.
• Your body may be producing a substance that causes the thyroid gland to make more hormone than your body needs.
• In rare cases there may be a tumor that makes the thyroid gland produce too much hormone.

Some thyroid gland problems may be inherited.

What are the Symptoms of Hyperthyroidism?

Symptoms include:

• anxiety, tiredness, or sleeplessness
• feeling shaky, having tremors
• feeling sweaty and hot, even though others around you are comfortable
• shortness of breath
• trouble focusing your eyes
• a bulging of one or both of your eyes
• double vision
• weight loss
• faster heart rate
• enlarged thyroid gland (goiter)
• increased appetite
• diarrhea

How is Hyperthyroidism Diagnosed?

Your health care provider will ask about your symptoms and examine you. You will have blood tests. These tests measure hormone levels and check thyroid gland function. Additional tests may be done to check the thyroid gland:

• A test called a radioactive iodine scan, or RAI uptake, shows if there are areas of the thyroid gland making more or less hormone than normal. For this test you will be given a very tiny amount of a radioactive form of iodine. Because the body uses iodine to make thyroid hormone, the radioactive iodine attaches to thyroid hormone being formed in the thyroid gland. A scan of radioactivity in the thyroid gland then shows areas of the gland making thyroid hormone. (The radioactive iodine becomes nonradioactive in 3 days.) Sometimes a radioactive chemical similar to iodine may be used instead of iodine.
• An ultrasound exam of the thyroid gland is another way to look at the thyroid gland. The ultrasound can show cysts or tumors in the gland and can be used to measure the size of the gland.

Eye problems related to thyroid disease may require specific tests such as a CT scan or an ultrasound to check the muscles that move the eye.

How is Hyperthyroidism Treated?

The options for treatment are medicine, radiation, or surgery. These treatments lower the amount of thyroid hormone in your body.

Antithyroid drugs reduce the amount of thyroid hormone made by the gland. They usually control hyperthyroidism in several weeks. Propylthiouracil (PTU), Propranolol, and Methimazole (Tapazole) are 3 commonly used drugs. You may need to keep taking these drugs for a year or longer.

A pill containing radioactive iodine is commonly used to treat some types of hyperthyroidism, especially if you have had hyperthyroidism more than once. The radiation is concentrated in the thyroid gland and destroys the cells that are making too much hormone. The main risk of this treatment is that your thyroid levels will become too low. A low level of thyroid hormone can be dangerous if it is not recognized. Your health care provider will watch your thyroid levels after this treatment. Low levels are easily treated with thyroid hormone medicine.

Surgery can be done to remove part or all of the overactive thyroid gland or to remove just a growth (tumor) in the gland. Surgery cures the disease 90% of the time. However, surgery has certain risks. The most common risk is that you will have low thyroid hormone levels after the surgery. You will then most likely need to take thyroid hormone medicine the rest of your life. Nerve damage is an uncommon risk of surgery. When it occurs, the nerve that is damaged is usually the one that goes to the voice box. The nerve damage may cause a soft or raspy voice.

Not everyone with thyroid disease has eye problems. Eye drops to keep the eyes moist are often necessary because the eyes dry out easily. Sometimes steroid medicine is used to treat the eye problems related to
thyroid disease. Surgery may be needed to treat eye muscle problems and eyelid problems, as well as crowding of the eye socket from swelling.

How Long Will the Effects of Hyperthyroidism Last?

The effects of hyperthyroidism usually last as long as thyroid hormone levels are too high. Sometimes the disease improves without treatment. However, it can cause heart failure and death if it is not treated.
Eye problems related to hyperthyroidism may continue even after the thyroid problem is treated.

How Can I Take Care of Myself?

• Follow the full treatment prescribed by your health care provider.
• Do not stop or change your thyroid medicine without first asking your health care provider.
• Have regular checkups according to your health care provider's recommendations.
• Contact your health care provider if your symptoms come back or get worse or you develop new symptoms that concern you.

How Can I Help Prevent Hyperthyroidism?

There is no known way to prevent this condition.

What is Hypothyroidism?

Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone. Too little hormone slows down chemical reactions in the body. This slowdown causes mental and physical changes.
The thyroid gland is located at the lower front of the neck. This gland takes iodine from the food you eat to make hormones called thyroxine (T4) and triiodothyronine (T3). The hormones control your metabolism (the process of turning the food you eat into energy). The thyroid gland is critical for maintaining body temperature and controlling heart rate, appetite, and digestive tract function. Too little hormone may cause you to gain weight. Also, your heartbeat slows down and your body temperature gets lower. Food moves through your intestines more slowly and your muscles contract more slowly.

How Does Hypothyroidism Occur?

Causes of hypothyroidism include:

• Hashimoto's disease (thyroiditis): This condition is an inflammation of the thyroid gland. It is a disorder of your immune system (your body's protection against infection).
• Thyroid surgery for complete or partial removal of the thyroid gland
• Viruses: They can infect the thyroid gland and cause it to produce too little hormone. These infections do not usually cause permanent hypothyroidism.
• Radiation treatment for hyperthyroidism (an overactive thyroid gland): Radioactive iodine is commonly used to treat an overactive thyroid gland. Radioactivity often destroys the gland. When this happens, the body needs synthetic thyroid hormone.

People who have had x-ray treatment for cancers of the head and neck may develop hypothyroidism if their thyroid was exposed to radiation during the cancer treatment.

• Iodine deficiency (rare): A lack of iodine in the diet is rare in the US because some foods, especially salt, contain added iodine.
• Medicines such as lithium, or too high a dosage of antithyroid medicine used to treat hyperthyroidism
• Problem with the pituitary gland (rare): The pituitary gland stimulates the thyroid gland to produce hormones. The pituitary may fail to stimulate the thyroid enough to meet your body's needs.
• Congenital hypothyroidism (rare): Some people are born without thyroid glands or with glands that cannot make thyroid hormone.

Anyone can have hypothyroidism, but it happens most often in women over age 40. Some thyroid problems are inherited.

What are the Symptoms of Hypothyroidism?

The gradual slowing of your body's processes can take months or even years, making it hard for you to recognize the disease.
Symptoms of hypothyroidism include:

• fatigue
• depression
• muscle weakness
• constipation
• weight gain
• feeling cold a lot of the time
• heavy and prolonged menstrual periods
• coarse, dry hair
• premature graying of hair in young adults
• thick, dry skin
• swollen eyelids
• deep, hoarse voice
• thick tongue
• thickened facial features
• slowed heart rate
• decreased sexual interest
• loss of hearing
• numbness and tingling hands

A condition that develops after several years of untreated hypothyroidism is called myxedema. Myxedema can cause you to become cold, slow to talk and move, and possibly drowsy. You might even fall into a coma.

How is Hypothyroidism Diagnosed?

Your health care provider will ask about your symptoms and examine you. If your provider thinks that you may have hypothyroidism, you will have blood tests. The tests will measure the levels of thyroid hormone and your pituitary's thyroid-stimulating hormone (TSH). TSH causes your thyroid gland to make thyroid hormone.

How is Hypothyroidism Treated?

Your health care provider will prescribe synthetic thyroid hormone medicine. You will most likely need to take the medicine every day for the rest of your life.

Most people need only small doses to replace their gland's normal output. After starting treatment, your health care provider will repeat the blood tests to be sure you are taking enough thyroid hormone. It may take several weeks to find the right dosage for you.

If you have coronary artery disease or are at risk for it, your provider will prescribe a smaller dose of hormone tablets at first. Replacing thyroid hormone too quickly can worsen coronary artery disease and, in some cases, can prompt a heart attack. Women prone to osteoporosis may have greater bone loss if they take too much thyroid hormone. For this reason your thyroid hormone blood level will be checked periodically for the rest of your life to make sure it is in the correct, normal range.

How Long Will the Effects of Hypothyroidism Last?

Usually hypothyroidism improves within a week after hormone therapy is begun. All symptoms go away within a few weeks. In most cases, however, you must continue this treatment for the rest of your life.
Mild hypothyroidism may cause no symptoms. If the disease progresses, however, it can become disabling over a long time if it is not treated. Untreated hypothyroidism may cause the following problems:

• enlargement of the heart and heart failure (rare)
• slowing of mental processes
• loss of consciousness

If the cause of hypothyroidism is thyroiditis and it is not treated, your thyroid gland may swell. This swelling, called a goiter, may cause a big bulge in your neck.

How Can I take Care of Myself?

Many people with hypothyroidism, especially older adults, don't seek medical treatment because they don't know they have a problem. They may accept their symptoms of fatigue, muscle weakness, dry skin, depression, feeling cold, and constipation as signs of aging. If you notice some of the symptoms of hypothyroidism, see your health care provider.
When you have hypothyroidism, be sure to:

• Follow your provider's instructions for taking your medicine.
• Get your thyroid hormone level checked when your provider suggests.
• Keep your follow-up appointments.

What Can Be Done to Help Prevent Hypothyroidism?

Except in the case when it is caused by a lack of iodine in the diet, hypothyroidism cannot be prevented.

What is the Thyroxine (T4) Test?

Thyroxine (T4) is a hormone produced by the thyroid gland. A test of the amount of T4 in the blood is a way to see how well the thyroid gland is working.

The thyroid gland is located at the lower front of the neck. Its main job is to make T4 and release it into the bloodstream. T4 circulates throughout the body, affecting all your organs. T4 regulates metabolism, like a thermostat regulates a furnace or air conditioner. The amount of T4 produced and released by the thyroid gland is controlled by the pituitary gland, which is located in the brain.
The test for T4 is one of several tests that can be done to check the functioning of the thyroid gland.

Why is the Thyroxine (T4) Test Done?

This test can show if your thyroid gland is producing too much or too little thyroid hormone. If you are taking thyroid hormone to make up for what your body does not produce, this test can help your health care provider know if you are taking the right amount of thyroid hormone.

How Do I Prepare for a Thyroxine (T4) Test?

• Make sure your health care provider knows about any medicines, herbs, or supplements that you are taking. Don't stop any of your regular medicines without first talking to your health care provider about it.
• Talk to your health care provider if you have any questions.

How is a Thyroxine (T4) Test Done?

A small amount of blood is taken from your arm with a needle. The blood is collected in tubes and sent to a lab.

Having this test will take just a few minutes of your time. There is no risk of getting AIDS, hepatitis, or any other blood-borne disease from this test.

How Will I Get My Thyroxine (T4) Test Result?

Ask your health care provider when and how you will get the result of your test.

What Does the Thyroxine (T4) Test Result Mean?

Your blood level of T4 may be higher than normal if:

• Your thyroid gland is producing too much thyroxine, a condition called hyperthyroidism.
• You are taking too much thyroid hormone replacement medicine.

Your blood level of thyroxine may be lower than normal because:

• Your thyroid gland is not producing enough thyroid hormone, a condition called hypothyroidism.
• You have hypothyroidism and you are not getting enough thyroid hormone replacement medicine.

Other factors can affect the level of thyroxine in your blood. For instance:

• Results from this test may be abnormal when you are sick for another reason.
• Because most of the thyroxine in the blood is attached to blood proteins, you may have an abnormal level of thyroxine if you have a blood protein level that is higher or lower than normal.
• Hormones such as estrogen affect protein levels in the blood and therefore affect thyroxine levels.
• Some medicines affect protein levels and may therefore affect thyroxine levels.
• Thyroxine contains iodine. Too little iodine sometimes can cause hypothyroidism (low T4) and too much can cause high levels of T4. It is hard to get too much iodine in your diet. However, some substances such as contrast materials (dye) used for special types of x-rays like angiograms and CT scans contain a lot of iodine. They can temporarily affect T4 levels in the blood.

Because of the many factors that can affect T4 levels, other thyroid function tests (such as a test measuring thyroid stimulating hormone, or TSH) are usually done in addition to or instead of the thyroxine test.

What if My Thyroxine (T4) Test Result is not Normal?

Test results are only one part of a larger picture that takes into account your medical history and current health. Sometimes a test needs to be repeated to check the first result. Talk to your health care provider about the result and ask questions.
If your test result is not normal, ask your health care provider:

• if you need additional tests
• what you can do to work toward a normal value
• when you need to be tested again