(TSH) blood test is used to check for thyroid gland problems. TSH is produced when the hypothalamusreleases a substance called thyrotropin-releasing hormone (TRH). TRH then triggers the pituitary gland to release TSH.TSH causes the thyroid gland to make two hormones:triiodothyronine (T3) and thyroxine (T4). T3 and T4 helpcontrol your bodys metabolism.
Why It Is Done*Find out whether the thyroid gland is workingproperly_An underactive thyroid gland (hypothyroidism)_An overactive thyroid (hyperthyroidism)*Find the cause of an underactive thyroid gland(hypothyroidism).
• Keep track of treatment with thyroid replacement medicine for people who have hypothyroidism.• Keep track of thyroid gland function in people who are being treated for hyperthyroidism. This treatment may include antithyroid medicine, surgery, or radiation therapy.• Double-check the diagnosis of an underactive thyroid gland in a newborn(congenital hypothyroidism).
How To PrepareTell your doctor if you have had any tests in which you weregiven radioactive materials or had X-rays that used iodine dyewithin the last 4 to 6 weeks. Your test results may not becorrect if you have had iodine contrast material before havinga thyroid-stimulating hormone (TSH) test.
How It Is DoneThe health professional drawing blood will:• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.• Clean the needle site with alcohol.• Put the needle into the vein. More than one needle stick may be needed.• Attach a tube to the needle to fill it with blood.• Remove the band from your arm when enough blood is collected.• Put a gauze pad or cotton ball over the needle site as the needle is removed.• Put pressure to the site and then put on a bandage.
TSH- Normal range Until 2002, the official TSH "normal range" that laboratories and most doctors used throughout the U.S. was a range of 0.5 to 5.0. Since late 2002, however, the American Association of Clinical Endocrinologists (AACE) and other professional groups have recommended a narrower range of .3 to 3.0.
Free T4 - Free Thyroxine Free T4 measures the free, unbound thyroxine levels in your bloodstream. Free T4 is typically elevated in hyperthyroidism, and lowered in hypothyroidism. Free or unbound T4 levels represent the level of hormone available for uptake and use by cells. Bound levels represent a circulating hormone that may not all be immediately available, because it is affected by other drugs, illness, and physical changes such as pregnancy. Because the free levels of T4 represent immediately available hormone, free T4 is thought to better reflect the patients hormonal status than total T4
Total T4/Total Thyroxine/Serum Thyroxine This test measures the total amount of circulating thyroxine in your blood.Thyroxine, a hormone produced by the thyroid, is also known as T4. A highvalue can indicate hyperthyroidism, a low value can indicate hypothyroidism.Total T4 levels can be elevated due to pregnancy, and other high estrogenstates, including use of estrogen replacement or birth control pills.
Total T3-Total Triiodothyronine Triiodothyronine is the active thyroidhormone, and is also known as T3. Total T3 istypically elevated in hyperthyroidism, andlowered in hypothyroidism.
Free T3 - Free TriiodothyronineFree T3 measures the free, unbound levels of triiodothyroninin your bloodstream. Free T3 isconsidered more accurate than Total T3. Free T3 is typically elevatedin hyperthyroidism, and lowered inhypothyroidism.
T3 &T4-Normal rangeT4: Normal Adult Range: 4 - 12 ug/dl OptimalAdult Reading: 8 ug/dlT3: Normal Adult Range: 27 - 47% Optimal AdultReading: 37 %
What does the test result mean?TSH T4 T3 InterpretationHigh Normal Normal Mild (subclinical) hypothyroidismHigh Low Low or Hypothyroidism normalLow Normal Normal Mild (subclinical) hyperthyroidismLow High or High or Hyperthyroidism normal normalLow Low or Low or Non-thyroidal illness; rare pituitary normal normal (secondary) hypothyroidism
Signs and symptoms of hyperthyroidism may include:• Increased heart rate• Anxiety• Weight loss• Difficulty sleeping• Tremors in the hands• Weakness• Diarrhea (sometimes)• Light sensitivity, visual disturbances• The eyes may be affected: puffiness around the eyes, dryness, irritation, and, in some cases, bulging of the eyes.
Symptoms of hypothyroidism may include:• Weight gain• Dry skin• Constipation• Cold intolerance• Puffy skin• Hair loss• Fatigue• Menstrual irregularity in women