T4 (thyroxine) Test

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What is a T4 (thyroxine) Test?

Definition

A T4 test measures the amount of the T4 hormone in the blood. T4 is produced by the thyroid gland. T4 levels are crucial, because T4 increases numerous enzymes that produce energy for the body. Alternative Name: Thyroxine quiz.

How the test is performed:

rake is drawn from a vein on the inside of the elbow or the bet on of the hand. The puncture locate is cleaned with antiseptic, and an elastic band is placed around the upper berth branch to apply pressure and restrict blood flow through the vein. This causes veins below the band to swell with blood. A phonograph needle is inserted into the vein, and the lineage is collected in an airtight phial or a syringe. During the routine, the band is removed to restore circulation. Once the rake has been collected, the phonograph needle is removed, and the puncture locate is covered to stop any run. For an baby or young child, the sphere is cleansed with antiseptic and punctured with a sharp needle or a lancet arch. The blood may be collected in a pipet ( little glass pipe ), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continue bleeding.

How to prepare for the test:

The health wish supplier may advise you to stop taking drugs that may affect the test ( see “ special considerations ” ). For infants and children : The homework you can provide for this test depends on your child ‘s age and experience. For specific information regarding how you can prepare your child, see the follow topics :

• infant test or procedure preparation (birth to 1 year)
• toddler test or procedure preparation (1 to 3 years)
• preschooler test or procedure preparation (3 to 6 years)
• schoolage test or procedure preparation (6 to 12 years)
• adolescent test or procedure preparation (12 to 18 years)

How the test will feel:

When the needle is inserted to draw rake, some people feel moderate pain, while others feel only a incision or bite sensation. Afterward, there may be some throbbing.

Why the test is performed:

This test may be performed as function of an evaluation of thyroid officiate. Thyroid routine is complex and depends on the carry through of many different hormones :

1. Thyroid-stimulating hormone (TSH) is a secreted by the pituitary gland.
2. TSH causes the thyroid gland to produce two more hormones, T4 (thyroxine) and T3 (triiodothyronine).
3. Finally, TSH itself is stimulated by another hormone, thyroid-releasing hormone (TRH), which is made by the hypothalamus.

In people with normal thyroid function, having enough T3 and T4 inhibits both TSH and TRH, which prevents the body from making besides much T3 and T4. Most T3 and T4 is transported by a protein called TBG ( thyroxine tie globulin ), but smaller amounts are found on prealbumin and albumin. When not bound to proteins, they are called “ dislodge ” T3 or T4.

Normal Values:

normal values vary among different laboratories. A typical convention stove is : 4.5 to 11.2 mcg/dL ( micrograms per deciliter ).

What abnormal results mean:

Greater-than-normal levels of T4 along with broken levels of TSH may indicate hyperthyroid conditions, such as :

• Graves’ disease
• toxic multinodular goiter
• subacute or chronic thyroiditis
• early Hashimoto’s disease
• iodine-induced hyperthyroidism
• germ cell tumors
• trophoblastic disease

Lower-than-normal levels of T4 may indicate :

• hypothyroidism (including Hashimoto’s disease, cretinism, myxedema, goitrous diseases, scleroderma, amyloid goiter, or hemochromatosis following neck irradiation for head and neck cancer)
• malnutrition or fasting
• illness throughout the body
• use of certain prescribed medication, including dexamethasone, propranolol, lithium, iodine, methimazole, propylthiouracil, interferon alfa, interleukin-2, and amiodarone

extra conditions under which the test may be performed :

• hypopituitarism
• hypothyroidism – primary
• hypothyroidism – secondary
• thyrotoxic periodic paralysis

Risks:

Risks associated with having lineage draw are slight :

• excessive bleeding
• fainting or feeling lightheaded
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins

Considerations:

Drugs that can increase T4 measurements include clofibrate, estrogens, methadone, amiodarone, and birth control pills. Drugs that can decrease T4 measurements include anabolic steroids, androgens, antithyroid drugs ( for model, propylthiouracil and methimazole ), lithium, diphenylhydantoin, propranolol, amiodarone, interferon alpha, and interleukin-2. Veins and arteries vary in size from one patient to another and from one side of the consistency to the other. Obtaining a rake sample distribution from some people may be more unmanageable than from others.

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