The TSH test, or thyroid-stimulating hormone, is an essential blood test to assess thyroid function. By measuring TSH levels, this test can detect hormonal imbalances, such as hyperthyroidism or hypothyroidism, and guide treatment. Let's discover its importance and how it works.
TSH means thyroid stimulating hormone. Another name for this is thyroid-stimulating hormone. A TSH test is a blood test that measures this hormone. A TSH level that is too high or too low can be a sign of a thyroid problem.
The thyroid is a small butterfly-shaped gland located at the front of your neck. Your thyroid produces hormones that control how your body uses energy. Thyroid hormones affect nearly every organ and control many important functions in your body. For example, they influence your breathing, heart rate, weight, digestion, and even your mood. If you don't have enough thyroid hormones in your blood, many of your body's functions will slow down. But if you have too many, many body functions will speed up.
Your thyroid is controlled by a gland in your brain called the pituitary gland. The pituitary gland produces thyroid-stimulating hormone (TSH). TSH tells your thyroid how many thyroid hormones it should produce.
If the thyroid hormone level in your blood is too low, your pituitary gland produces higher amounts of TSH to tell your thyroid to work harder. If your thyroid hormone level is too high, the pituitary gland makes little or no TSH. By measuring the level of TSH in your blood, you can determine if your thyroid is producing the right level of hormones.
Other names: thyroid-stimulating hormone test, thyrotropic hormone
A TSH test is used to determine how well your thyroid is functioning. It can indicate whether you have hyperthyroidism (too much thyroid hormone) or hypothyroidism (too few thyroid hormones) in your blood. But a TSH test can't show what's causing a thyroid problem.
If you are taking prescription thyroid hormone medications because of hypothyroidism or because you have had your thyroid removed, you will have regular TSH tests to check your thyroid hormone levels. These tests are done to make sure you are taking the correct dose of medication. TSH tests are also used to monitor your thyroid hormone levels after treatment for hyperthyroidism. Â
You may need a TSH test if you have symptoms of too much or too little thyroid hormone in your blood.
Hyperthyroidism is also called an overactive thyroid. Having more thyroid hormones than you need speeds up your body's functions and causes symptoms that can vary from person to person. Symptoms may include:
Adults over the age of 60 may have different symptoms than young adults. For example, they may lose their appetite or withdraw from others. Sometimes it can be mistaken for depression or dementia.
Hypothyroidism (too few thyroid hormones) is also called an underactive thyroid. Not having enough thyroid hormone slows down your body's functions and causes symptoms that can vary from person to person. Symptoms may include:
Since hypothyroidism develops slowly, many people do not notice the symptoms of the disease for months or even years.
You may also have a TSH test and other tests to help diagnose unusual bumps or lumps on your thyroid. The tests will help your healthcare professional check for thyroid cancer or thyroid nodules (growths on your thyroid that aren't cancerous).
A health professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected in a test tube or bottle. You may feel a slight prick when the needle goes in or out. This usually takes less than five minutes.
You may need to stop taking some medications before this test, so let your provider know everything you are taking. But don't stop taking medication unless asked to do so by your provider. If your healthcare professional has ordered more blood tests, you may need to fast (not eat or drink) for several hours prior to the test. Your provider will let you know if there are any special instructions.
There is very little risk in taking a blood test. You may feel a slight pain or bruise where the needle was inserted, but most symptoms go away quickly.
Your TSH test results can show whether your thyroid is making too much or too little hormone. But the test can't explain why your TSH levels may be too high or too low.
If your test results are not normal, your health care provider will likely order additional thyroid blood tests to determine the cause of your thyroid problem. These blood tests may include:
In some cases, an abnormal TSH result may be a sign of a problem with the pituitary gland, but that doesn't happen often.
Learn more about lab tests, reference ranges, and understanding results.
Your TSH level may be high or low even when your thyroid is healthy. For example, the following may affect your TSH level:
Newborn babies are routinely screened with a TSH test to check if they were born with hypothyroidism (congenital hypothyroidism).
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