Thyroid Stimulating Hormone TSH

Also Known as:   TSH, Thyrotropin, Thyrotropic Hormone
 

What is a thyroid stimulating hormone (TSH blood test)?

This test measures thyroid-stimulating hormone (TSH) levels in the blood. TSH Blood test is a hormone that stimulates the thyroid gland to make other hormones, such as thyroxine (T4) and triiodothyronine (T3). Your metabolism, or how your body consumes and stores energy, is controlled by T3 and T4. TSH is produced by the pituitary gland and acts on the thyroid gland by attaching to the TSH receptor. The pituitary gland is also called the "master gland" since it produces various hormones that influence other glands in the body. Too low or too high T3 and T4 hormone levels are detected by the pituitary gland. It will produce more or less TSH in response, stimulating your thyroid gland to make the right amount of hormones.

If your thyroid is underactive, your TSH levels may be elevated as your pituitary gland tries to stimulate the thyroid to generate more T3 and T4. Your TSH may be abnormally low if your thyroid is overactive because your pituitary gland stops producing TSH when your thyroid hormone levels are too high.

What is the TSH Blood test used for? 

Your TSH Blood test level informs you whether or not your thyroid gland is in proper working order. TSH is commonly assessed as part of a thyroid panel, including tests of thyroid hormones. Additional thyroid tests may be requested if TSH is checked alone and the result is abnormal.TSH testing can be used for a variety of reasons, including:

• Determining if the thyroid gland is underactive or overactive.
• Screening of thyroid disease before symptoms appear, especially in newborns.
• Evaluation of a thyroid nodule (a lump on the thyroid gland). 
• Evaluation of goiter (enlargement of the thyroid gland). 
• Diagnosis of thyroid-related diseases such as Hashimoto's thyroiditis, Graves' disease, and thyroid cancer.
• Monitoring a patient's response to treatment for hypothyroidism, hyperthyroidism, or another thyroid condition.

Why and when do you need TSH Blood test?

When doctors suspect a patient has a thyroid problem, TSH Blood test is often ordered initially. All patients with signs of thyroid disease should have their TSH levels checked. Hypothyroidism and hyperthyroidism are both common thyroid conditions. Your doctor may recommend a TSH or a thyroid panel test if you have signs of these diseases. Hypothyroidism causes the following symptoms:

• Fatigue
• Pain in muscles and joints
• Slow heart rate
• Gain in weight
• Skin dryness
• Feeling of cold
• Constipation
• Menstrual irregularities
• Depression
• Fertility issues
• Thin and/or dry hair 

Symptoms of hyperthyroidism include:

• Weight loss
• Anxiety and irritability
• Palpitations
• Bulging eyes
• Increased appetite
• Mood swings
• Irregular heartbeat
• Goiter (enlarged thyroid gland)
• Heat intolerance
• Diarrhea.
• Hand tremors
• Trouble sleeping
• Irregular periods
• Muscle weakness

TSH Blood test is also used to evaluate patients with goiter, thyroid nodules, thyroid cancer, Graves' disease, or Hashimoto's thyroiditis and those suspected of having additional thyroid problems. Routine thyroid screening in people without symptoms is also recommended. Early detection and treatment of the disease are most effective as it helps patients avoid future medical problems. 

Some experts suggest screening only adults at a higher risk of thyroid disorders, such as those with autoimmune disorders or a family history of thyroid disease. Because thyroid problems might complicate pregnancy, some women should be screened with a TSH test throughout pregnancy.

Congenital hypothyroidism, or an underactive thyroid at birth, is routinely screened in newborn babies. The symptoms of hypothyroidism in infants can be successfully treated if discovered early. The symptoms of hypothyroidism in infants can be successfully treated if found early.

TSH levels in the blood will also be checked regularly in people taking replacement thyroid hormones for hypothyroidism or who have had thyroid surgery. Doctors may change the drug dose as necessary by monitoring TSH. TSH testing can also be used to keep track of patients who have been treated for hyperthyroidism.

What kind of sample is required for the TSH Blood test?

A healthcare provider will use a small needle to obtain a blood sample from a vein in your arm. A small amount of blood will be collected into a test tube or vial once the needle is inserted. When the needle goes in or out, it may sting a little. It usually takes less than five minutes to complete this process.

Do you need to prepare for the TSH Blood test?

This test does not require any special preparation. However, you should always check with your doctor's office ahead of time to see if you need to follow any pre-test instructions given to you. It's always healthy to inform your doctor about any medications you're taking, as some of them may interfere with your test results. For example, If you're using biotin or Vitamin B7 supplements, you should stop taking them at least two days before your TSH test since they can affect the accuracy of your results.

Are there any risks to TSH Blood test?

There are no significant risks of having a tsh blood test. You or your child may experience minor pain or bruising where the needle was inserted, but most symptoms disappear quickly.

What do the test results mean?

Your test results will show if your blood level of thyroid-stimulating hormone (TSH) is above or below normal limits, often known as the reference range. Milli-international units per liter (mIU/L) are a common unit of measurement. The reference ranges will differ slightly based on the testing laboratory. The TSH reference range for adults is 0.5–4.0 mIU/L, according to the American Board of Internal Medicine. However, because reference ranges differ by laboratory, it's crucial to consult your doctor about your test results reference range.

When assessing a patient's TSH, doctors may consider a variety of factors, including:

• TSH levels in patients above the age of 80 tend to be higher. Most older patients with TSH Blood test levels that are somewhat higher than normal do not have any health problems.
• Changes in thyroid hormones occur during pregnancy. TSH is likely to be slightly lower than normal during the first trimester, then gradually rise.
• People who are very sick with disorders unrelated to the thyroid gland may also have low TSH Blood tests.
• Other tests, such as free T4 and thyroid antibodies, may impact how a doctor interprets a TSH result.

TSH Blood test levels higher than normal may suggest that the thyroid is underactive. TSH levels below normal can indicate that the thyroid gland produces too much thyroid hormone. An abnormal TSH level might occur when the pituitary gland isn't functioning correctly.
 
If your TSH test results are abnormal, your thyroid function may be further tested. A thyroid panel, which includes numerous thyroid hormone tests, may be ordered by your doctor. Thyroid antibody testing may also be performed on some patients. Antibody tests can identify whether an overactive or underactive thyroid is caused by autoimmune diseases such as Graves' disease or Hashimoto's thyroiditis.
 
Related tests: Thyroid Panel, T4 Test, T3 Test, Thyroid Antibodies

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our lab test content,  blogs, and articles when new information becomes available. Last reviewed by Dr. Tayyab Saeed Akhter on December 19th, 2023.