What Is a Blood Test?

By taking and testing a small sample of a person’s blood, doctors can check for many kinds of diseases and conditions. Blood tests help doctors check how the body’s organs are working and see if medical treatments are helpful.

To help your child get ready for a blood test, find out if they need to fast (not eat or drink) or should stop taking medicines before the test. Explain what to expect during the test. If your child is anxious about it, work together on ways to stay calm.

What Is TSH?

Thyroid stimulating hormone (TSH) is made by the pituitary, a pea-sized gland at the base of the brain.

When the thyroid gland doesn’t make enough of two important hormones, triiodothyronine (T3) and thyroxine (T4), it is called hypothyroidism, or underactive thyroid. In response, the pituitary gland makes more TSH to try to stimulate the thyroid so it will make more hormones. A pituitary gland that’s not working well can make too little TSH, which also can lead to hypothyroidism.

If the thyroid gland makes too much T3 or T4, it can cause hyperthyroidism, or overactive thyroid. Then, the pituitary gland makes less TSH to try to decrease the thyroid's production of the hormones.

Why Are TSH Tests Done?

Doctors order TSH tests to:

• diagnose a thyroid disorder
• monitor treatment of thyroid problems
• see how well the thyroid or pituitary are working

TSH tests are usually included in newborn screening tests in most states. This lets doctors find and treat congenital (present at birth) hypothyroidism right away.

Tell the doctor about any medicines your child takes since some can affect the test results.

What if I Have Questions?

If you have questions about the TSH test or what the results of the test mean, talk to your doctor.