TSH (Thyroid Stimulating Hormone) Test

Written by Cindie Slightam | Published on August 15, 2012
Medically Reviewed by Brenda B. Spriggs, MD, MPH, FACP

What is a Thyroid Stimulating Hormone Test?

A TSH test is used to measure the amount of thyroid stimulating hormone (TSH) in your blood. It will help your doctor determine if you need medication to treat hyperthyroidism (overactive thyroid gland) or hypothyroidism (underactive thyroid gland). It is sometimes called a “thyrotropin test.”

TSH is a hormone produced by the pituitary gland that tells the thyroid to make and release thyroxine (T4) and triiodothyronine (T3). Together, these essential hormones help control the rate at which the body uses energy.

Why Is a TSH Test Ordered?

Your doctor will order this test if you have signs of hyperthyroidism, hypothyroidism, or an enlarged thyroid. The test may also be ordered to monitor ongoing treatment of these conditions.

Symptoms of hyperthyroidism (when your thyroid gland makes too much thyroid hormone) include:

  • difficulty sleeping
  • hand tremors
  • irritated eyes and light sensitivity
  • nervousness
  • weight loss
  • rapid heart rate

Symptoms of hypothyroidism (when your thyroid gland makes too little TSH) include:

  • dry skin
  • constipation
  • sensitivity to the cold
  • fatigue
  • hair loss
  • irregular menstrual periods
  • puffy skin
  • weight gain

A TSH level test is also used to screen newborns for an underactive thyroid and to diagnose and monitor female infertility problems. Occasionally, it is used to evaluate pituitary gland function.

How is the TSH Level Test Performed?

The TSH test involves analyzing a sample of your blood in a laboratory. To obtain a blood sample, a nurse will draw blood from a vein in your arm or the back of your hand.

First, the site will be cleaned with an antiseptic. Then the nurse will wrap a band around your arm to apply pressure to the area and gently insert a needle into the vein. Your blood will be collected in a tube attached to the needle. Once the tube is full, the band and the needle will be removed. Pressure can be applied to the puncture site with a cotton ball or gauze to stop any excess bleeding.

For infants and small children, a lancet (a small instrument similar to a scalpel) is used to puncture the skin. The blood sample collects in a small glass pipette or on a test strip or slide. A bandage may be placed over the area if there is any bleeding.

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