A thyroid stimulating hormone (TSH) test is a common blood test used to evaluate
how well the thyroid gland is working. The thyroid gland is located at the lower front
of the neck. TSH is produced by the pituitary, a pea-sized gland located at the base
of the brain.
When the thyroid gland isn't producing enough thyroid hormone (a condition called
hypothyroidism), the pituitary gland produces more TSH in an attempt to stimulate
the thyroid and increase its production of thyroid hormones. If the pituitary gland
isn't functioning properly, it may produce too little TSH, and this can result in
hypothyroidism as well.
If the thyroid gland is producing too much thyroid hormone (a condition called
hyperthyroidism), the pituitary gland produces less TSH in an attempt to decrease
the thyroid's production of thyroid hormones.
Symptoms of hypothyroidism in children include tiredness or fatigue, dry skin,
constipation, slow growth, and delayed pubertal development. Hyperthyroidism can cause
unexpected weight loss, a rapid or irregular heartbeat, sweating, nervousness, and
In both hypothyroidism and hyperthyroidism, the child may develop a goiter —
a lump in the neck due to enlargement of the thyroid gland. Both conditions are treatable.
Why It's Done
TSH testing is used to:
diagnose and monitor the treatment of a thyroid disorder
help evaluate pituitary gland function
Your doctor may order a TSH test if your child has symptoms of hyperthyroidism
or hypothyroidism, or shows signs of an enlarged thyroid gland. The TSH test also
may be ordered at regular intervals to monitor the effectiveness of treatment if your
child is being treated for a thyroid disorder.
TSH tests are routinely ordered for newborns in many states as part of the screening
program to enable the prompt diagnosis and treatment of infants with congenital (present
at birth) hypothyroidism.
Your child doesn't have to fast or limit activity before the test. However, some
medications may affect test results. Check with your doctor to see if you should discontinue
any medications until after the test. Extreme stress and acute or chronic illness
also can affect TSH test results.
On the day of the test, it may help to have your child wear a T-shirt or short-sleeved
shirt to allow easier access for the technician who will be drawing the blood.
A health professional will usually draw the blood from a vein. For an infant, the
blood may be obtained by puncturing the heel with a small needle (lancet). If the
blood is being drawn from a vein, the skin surface is cleaned with antiseptic and
an elastic band (tourniquet) is placed around the upper arm to apply pressure and
cause the veins to swell with blood. A needle is inserted into a vein (usually in
the arm inside of the elbow or on the back of the hand) and blood is withdrawn and
collected in a vial or syringe.
After the procedure, the elastic band is removed. Once the blood has been collected,
the needle is removed and the area is covered with cotton or a bandage to stop the
bleeding. Collecting the blood for the test will only take a few minutes.
What to Expect
Collecting a blood sample is only temporarily uncomfortable and feels like a quick
pinprick. Afterward, there may be some mild bruising, which should go away in a day
Getting the Results
The blood sample will be processed by a machine. The results are commonly available
within a day or two.
Whether your child's results are high or low, an abnormal TSH usually indicates
an excess or deficiency in the amount of thyroid hormone available to his or her body.
It does not, however, indicate what the specific problem is. To determine the cause,
your doctor will usually do additional testing, such as measurement of the blood levels
of the hormones produced by the thyroid gland itself.
The TSH test is considered a safe procedure. However, as with many medical tests,
some problems can happen with having blood drawn. These include:
fainting or feeling lightheaded
hematoma (blood accumulating under the skin causing a lump or bruise)
pain associated with multiple punctures to locate a vein
Helping Your Child
Having a blood test is relatively painless. Still, many children are afraid of
needles. Explaining the test in terms your child can understand might help ease some
of the fear.
Allow your child to ask the technician any questions he or she might have. Tell
your child to try to relax and stay still during the procedure, as tensing muscles
and moving can make it harder and more painful to draw blood. It also may help if
your child looks away when the needle is being inserted into the skin.
If You Have Questions
If you have questions about the TSH test procedure, speak with your doctor. You
can also talk to the technician before the procedure.