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Medical Health Encyclopedia
T4 test
From Healthscout's partner site on breast cancer, HealthCentral.com
T4 (thyroxine) is a hormone produced by the thyroid gland. A laboratory test can be done to measure the amount of T4 in your blood. Alternative Names
Thyroxine test How the test is performed Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood. Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding. ![]() In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding. How to prepare for the test Your health care provider will tell you, if necessary, to stop taking drugs that may interfere with the test. Drugs that can increase T4 measurements include:
Drugs that can decrease T4 measurements include:
This list may not include all medications. How the test will feel When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing. Why the test is performed This test is done to check your thyroid function. Thyroid function is complex and depends on the action of many different thyroid hormones, including thyroid-stimulating hormone (TSH) and T3 (triiodothyronine). Your doctor may order this test if you have signs of a thyroid disorder, including:
Review Date: 04/20/2010 A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). ![]() | |||||||||||||||||
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