Levels of TSH in the blood increase gradually during the second and third trimesters, but they remain lower than normal levels in women who are not pregnant. Doctors carefully monitor TSH levels throughout pregnancy. Having unusually high or low levels can affect the risk of miscarriage and cause pregnancy-related complications , such as:.
The following table shows TSH levels for children by age, according to a study from based on data from healthy children:. High TSH levels indicate hypothyroidism. People develop hypothyroidism when their thyroid produces low levels of hormones.
When the thyroid gland does not produce enough hormones, the pituitary gland produces more TSH to compensate. Symptoms of hypothyroidism include:. Low TSH levels indicate hyperthyroidism. This is also known as an overactive thyroid. If the thyroid gland is secreting levels of hormones that are too high, the pituitary gland produces less TSH. Symptoms of hyperthyroidism include:.
The TSH test involves a healthcare professional drawing blood from a vein in the inner arm. They then send the blood sample to a laboratory for testing. Usually, people do not need to prepare for a TSH test.
However, if the doctor is testing the blood for more than one issue, a person may need to fast or prepare in another way. The doctor will provide this information beforehand.
If a person has abnormally high or low TSH levels, the doctor needs to run at least one other diagnostic test to identify the underlying cause. These tests look at levels of specific thyroid hormones and antibodies. Doctors can treat hypothyroidism with medications, such as levothyroxine, that replace the missing thyroid hormones. A person should take this medication once a day, or as prescribed by their doctor.
The doctor will monitor how well the treatment is working by running additional blood tests every few months. According to the Food and Drug Administration FDA , people should take levothyroxine once a day: in the morning and on an empty stomach, at least half an hour before eating. They recommend that a person tells their doctor if they eat soybean flour, walnuts, dietary fiber, or cottonseed meal, as these can affect how the body processes levothyroxine.
Treatments for hyperthyroidism focus on reducing thyroid hormone levels to prevent long term health complications. A person may need to take beta-blockers and antithyroid medications. Another effective treatment is radioiodine therapy. This involves taking a capsule or liquid that contains radioactive iodine, which destroys cells that produce thyroid hormones. However, people who take radioiodine therapy may develop hypothyroidism in the future.
Surgical removal of the thyroid gland can treat severe hyperthyroidism. Sometimes, an ultrasound or the thyroid gland may also be ordered. There are treatments for each of these diseases. Follow your entire healthcare provider's instructions regarding laboratory testing for your disease, and follow up care depending on the results. If you have an overactive thyroid hyperthyroidism your doctor or healthcare provider may prescribe:.
If you have an underactive thyroid hypothyroidism your doctor or healthcare provider may prescribe:. Return to list of Blood Test Abnormalities.
Note: We strongly encourage you to talk with your health care professional about your specific medical condition and treatments. The information contained in this website is meant to be helpful and educational, but is not a substitute for medical advice. For information about the 4th Angel Mentoring Program visit www.
Toggle navigation. Spanish About Chemocare. Thyroid Function Tests. Here begins a complex hormone process: Once converted to iodine, your serum T4, called thyroxine hormone is formed. The thyroxine hormone is converted into a more potent or active form of hormone, your serum blood T3. This is also called triiodothyronine. These T4 and T3 hormones will circulate in your body, and regulate your metabolism.
Your FT4I free thyroxine index is another test used to measure your thyroid function. All of these thyroid function tests are all indicators of your thyroid gland function. Thyroid stimulating hormone TSH , is the most common test that is ordered if your healthcare provider thinks that your thyroid gland is not functioning properly. A gland, called the pituitary gland, secretes TSH.
TSH is responsible for taking iodide out of your blood stream, and into your thyroid gland. TSH is also responsible for production of the thyroid hormone. If you have an abnormally high or low TSH level, whether it is elevated or decreased, your healthcare provider may order serum blood T3, serum T4, or FT4I tests.
While there are many other tests that can be performed, these are the most common tests for diagnosing hyperthyroid or hypothyroid , and the most specific indicators as to how well your thyroid gland is functioning. Based on your laboratory values of your thyroid function tests, and your symptoms, your healthcare provider may decide whether or not to treat your disease, whether it be hyperthyroidism or hypothyroidism.
In cases of hyperthyroidism, your TSH level will be decreased, because there is too much thyroid hormone in your blood.
This is the most common cause of hyperthyroidism. Standard treatment for hypothyroidism involves daily use of the synthetic thyroid hormone levothyroxine Levo-T, Synthroid, others. This oral medication restores adequate hormone levels, reversing the signs and symptoms of hypothyroidism.
You'll likely start to feel better soon after you start treatment. The medication gradually lowers cholesterol levels elevated by the disease and may reverse any weight gain. Treatment with levothyroxine will likely be lifelong, but because the dosage you need may change, your doctor is likely to check your TSH level every year. To determine the right dosage of levothyroxine initially, your doctor generally checks your level of TSH after six to eight weeks.
After that, blood levels are generally checked six months later. Excessive amounts of the hormone can cause side effects, such as:.
If you have coronary artery disease or severe hypothyroidism, your doctor may start treatment with a smaller amount of medication and gradually increase the dosage. Progressive hormone replacement allows your heart to adjust to the increase in metabolism.
Levothyroxine causes virtually no side effects when used in the appropriate dose and is relatively inexpensive. If you change brands, let your doctor know to ensure you're still receiving the right dosage. Also, don't skip doses or stop taking the drug because you're feeling better. If you do, the symptoms of hypothyroidism will gradually return.
Certain medications, supplements and even some foods may affect your ability to absorb levothyroxine. Talk to your doctor if you eat large amounts of soy products or a high-fiber diet or you take other medications, such as:.
Levothyroxine is best taken on an empty stomach at the same time every day. Ideally, you'll take the hormone in the morning and wait an hour before eating or taking other medications. If you take it at bedtime, wait four hours after your last meal or snack. If you have subclinical hypothyroidism, discuss treatment with your doctor.
For a relatively mild increase in TSH, you probably won't benefit from thyroid hormone therapy, and treatment could even be harmful. On the other hand, for a higher TSH level, thyroid hormones may improve your cholesterol level, the pumping ability of your heart and your energy level. Although most doctors recommend synthetic thyroxine, natural extracts containing thyroid hormone derived from the thyroid glands of pigs are available. These products contain both thyroxine and triiodothyronine.
Synthetic thyroid medications contain thyroxine only, and the triiodothyronine your body needs is derived from the thyroxine. Extracts are available by prescription only and shouldn't be confused with the glandular concentrates sold in natural foods stores. These products aren't regulated by the Food and Drug Administration, and their potency and purity isn't guaranteed.
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