Thyroid-stimulating hormone (tsh) test

A thyroid-stimulating hormone (TSH) test is one of several blood tests used to check for thyroid gland problems. TSH causes the thyroid gland to make other important hormones that help control your body's metabolism.

This test is done to:

• Find out if the thyroid gland is working as it should.
• Find out if a problem with the thyroid is causing symptoms such as growth problems, tiredness, weight gain, or weight loss.
• Keep track of how well thyroid treatment is working.
• Test a newborn to find out if his or her thyroid gland is working as it should.

Blood test

A health professional uses a needle to take a blood sample, usually from the arm.

Heel stick

A heel stick is used to get a blood sample from a baby. The baby's heel is poked, and several drops of blood are collected. Your baby may have a tiny bruise where the heel was poked.

In general, there's nothing you have to do before this test, unless your doctor tells you to.

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

Results are usually available in 2 to 3 days.

A slightly high TSH value may not require treatment. The doctor will consider any symptoms you might have along with other test results to determine if treatment is needed.

High values

High TSH levels may be caused by:

• An underactive thyroid (hypothyroidism). Hashimoto's thyroiditis is the most common cause of primary hypothyroidism.
• A pituitary gland tumor that is making too much TSH. This is uncommon.
• Not taking enough thyroid hormone medicine for treatment of an underactive thyroid gland.

Low values

Low TSH levels may be caused by:

• An overactive thyroid gland (hyperthyroidism). Causes of hyperthyroidism include Graves' disease, a type of goiter (toxic multinodular goiter), and a noncancerous (benign) tumor called a toxic nodule.
• Damage to the pituitary gland that prevents it from making TSH (a condition called secondary hypothyroidism).
• Taking too much thyroid medicine for treatment of an underactive thyroid gland.
• Pregnancy during the first trimester.