What Is a Thyroid-Stimulating Hormone Test?
A thyroid-stimulating hormone (TSH) test measures the amount
of TSH in the blood. TSH is produced by the pituitary gland, which is located
at the base of your brain. It’s responsible for regulating the amount of
hormones released by the thyroid.
The thyroid is small, butterfly-shaped gland located in the
front of the neck. It’s an important gland that creates three primary hormones:
- triiodothyronine (T3)
- thyroxine (T4)
The thyroid controls numerous different bodily functions,
including metabolism and growth, through the release of these three hormones.
Your thyroid will produce more hormones if your pituitary
gland produces more TSH. In this way, the two glands work together to make sure
the right amount of thyroid hormones are produced. However, when this system is
disrupted, your thyroid can produce either too many or too few hormones.
A TSH test is often performed to determine the underlying
cause of abnormal thyroid hormone levels. It’s also used to screen for an
underactive or overactive thyroid gland. By measuring the level of TSH in the
blood, your doctor can determine how well the thyroid is working.
Why Is a Thyroid-Stimulating Hormone Test Performed?
Your doctor may order a TSH test if you’re experiencing
symptoms of a thyroid disorder. Thyroid diseases can be categorized as either hypothyroidism
is a condition in which the thyroid produces too few hormones, causing metabolism
to slow down. The symptoms of hypothyroidism include fatigue, weakness, and
difficulty concentrating. The following are some of the most common causes of
- Hashimoto’s disease is an autoimmune condition
that causes the body to attack its own thyroid cells. As a result, the thyroid is
unable to produce a sufficient amount of hormones. The condition doesn’t always
cause symptoms, so it can progress over several years before it causes
- Thyroiditis is an inflammation of the thyroid
gland. It’s often caused by a viral infection or an autoimmune disorder, such
as Hashimoto’s disease. This condition interferes with thyroid hormone
production and eventually leads to hypothyroidism.
- Postpartum thyroiditis is a temporary form of thyroiditis
that may develop in some women after childbirth.
- The thyroid uses iodine to produce hormones. An
iodine deficiency can lead to hypothyroidism. Iodine deficiency is extremely
rare in the United States due to the use of iodized salt. However, it’s more common
in other regions of the world.
is a condition in which the thyroid produces too many hormones, causing the
metabolism to speed up. Symptoms of hyperthyroidism include increased appetite,
anxiety, and difficulty sleeping. The following are some of the most common
causes of hyperthyroidism:
- Graves’ disease is a common disorder in which
the thyroid becomes larger and produces an excessive amount of hormones. The
condition shares many of the same symptoms as hyperthyroidism and often
contributes to the development of hyperthyroidism.
- Thyroiditis eventually leads to hypothyroidism, but
in the short term, it can also trigger hyperthyroidism. This may occur when the
inflammation causes the thyroid to produce too many hormones and release them
all at once.
- Having too much iodine in the body can cause the
thyroid to become overactive. This typically occurs as a result of continuously
using medications that contain iodine. These medicines include some cough
syrups as well as amiodarone,
which is used to treat heart arrhythmias.
- Thyroid nodules are benign lumps that sometimes
form on the thyroid. When these lumps begin to increase in size, they may
become overactive and the thyroid may start producing too many hormones.
How Do I Prepare for a Thyroid-Stimulating Hormone Test?
The TSH test doesn’t require any special preparation.
However, it’s important to tell your doctor if you’re taking medications that
might interfere with the accuracy of the TSH measurement. Some medications that
could interfere with a TSH test are:
You may need to avoid using these drugs before the test.
However, don’t stop taking your medications unless your doctor tells you to do
How Is a Thyroid-Stimulating Hormone Test Performed?
A TSH test involves taking a sample of blood. The blood is
typically drawn from a vein that’s inside the inner elbow.
A healthcare provider will perform the following procedure:
they’ll clean the area with an antiseptic or other sterilizing solution.
then tie an elastic band around your arm to make the veins swell with blood.
they find a vein, they’ll insert a needle into the vein to draw blood. The
blood will be collected in a small tube or vial attached to the needle.
they draw enough blood, they’ll remove the needle and cover the puncture site with
a bandage to stop any bleeding.
The entire procedure should only take a few minutes to
complete. The blood sample will be sent to a lab for analysis. Once your doctor
receives the test results, they’ll schedule an appointment with you to discuss
the results and explain what they may mean.
What Do the Results of a Thyroid-Stimulating Hormone Test Mean?
The normal range of TSH levels is 0.4 to 4.0 milli-international
units per liter. If you’re already being treated for a thyroid disorder, the normal
range is 0.5 to 3.0 milli-international units per liter.
A value above the normal range usually indicates that the thyroid
is underactive. This indicates hypothyroidism. When the thyroid isn’t producing
enough hormones, the pituitary gland releases more TSH to try to stimulate it.
A value below the normal range means that the thyroid is
overactive. This indicates hyperthyroidism. When the thyroid is producing too
many hormones, the pituitary gland releases less TSH.
Depending on the results, your doctor may want to perform
additional tests to confirm the diagnosis.