免费T4测试

定义

T4 (thyroxine) is the main hormone produced by the thyroid gland. A laboratory test can be done to measure the amount of free T4 in your blood. Free T4 is the thyroxine that is not attached to a protein in the blood.

选择的名字

Free thyroxine test; Thyroxine test by equilibrium dialysis

如何执行测试

A 血液样本 是必要的.

如何准备考试

Your health care provider will tell you if you need to stop taking any medicines that may affect the test result. In general, test results are not affected by other medicines you may be taking. However, certain supplements including biotin (vitamin B7) can affect the results. Tell your provider if you are taking biotin.

怀孕和某些疾病, 包括肾脏和肝脏疾病, can also affect the results of this test.

考试的感觉如何

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. 这很快就会消失.

为什么要进行测试

Your provider may recommend this test if you have signs of a thyroid disorder, 包括:

• Abnormal findings of other thyroid blood tests, such as TSH or T3
• 疾病的症状 甲状腺功能亢进
• 疾病的症状 不够甲状腺
• Hypopituitarism -- when the pituitary gland does not produce enough of its hormones, including the hormone which stimulates the thyroid
• 肿块或结节 在甲状腺
• Enlarged or irregular thyroid gland
• 怀孕的问题

This test is also used to monitor people who are being treated for thyroid problems.

正常的结果

典型的正态范围是0.9 to 2.3 nanograms per deciliter (ng/dL), or 12 to 30 picomoles per liter (pmol/L).

Normal value ranges may vary slightly among different laboratories. Some laboratories use different measurements or may test different specimens. Talk to your provider about the meaning of your specific test results.

The normal range is based on a large population and is not necessarily normal for an individual. You may be having symptoms of hyperthyroidism or hypothyroidism even though your free T4 is in the normal range. The TSH test may help determine if your symptoms are related to thyroid disease. Talk to your provider about your symptoms.

异常结果意味着什么

To fully understand results of the free T4 test, results of other thyroid blood tests, 比如TSH和T3, 可能需要.

Test results may also be affected by pregnancy, 雌激素水平, 肝脏问题, 更严重的全身疾病, and inherited changes in a protein that binds T4.

A higher than normal level of T4 may be due to conditions that involve an 甲状腺功能亢进, 包括:

• 格雷夫斯病
• Taking too much thyroid hormone medicine
• 甲状腺炎
• Toxic goiter or toxic thyroid nodules
• Some tumors of the testes or ovaries (rare)
• Getting medical imaging tests with contrast dye that contains iodine (rare, and only if there is a problem with the thyroid)
• Eating a lot of foods that contain iodine (very rare, and only if there is a problem with the thyroid)

A lower than normal level of T4 may be due to:

• 甲状腺功能减退 (including Hashimoto disease and other disorders involving an 不够甲状腺)
• 严重急性疾病
• 营养不良 或禁食
• 某些药物的使用

风险

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a 血液样本 from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

• 大出血
• 昏厥或感到头晕
• 多次穿刺定位静脉
• Hematoma (blood buildup under the skin)
• Infection (a slight risk any time the skin is broken)

参考文献

Guber HA, Oprea M, Russell YX. 内分泌功能评价. 见:McPherson RA, Pincus MR，编辑. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24日艾德. Philadelphia, PA: Elsevier; 2022:chap 25.

韩森J，雷文P. Endocrinology and the reproductive system. 见:Niash J, Syndercombe D，主编. 医学科学. 3日艾德. Philadelphia, PA: Elsevier; 2019:chap 10.

Salvatore D, Cohen R, Kopp PA, Larsen PR. Thyroid pathophysiology and diagnostic evaluation. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. 威廉斯内分泌学教科书. 14日艾德. Philadelphia, PA: Elsevier; 2020:chap 11.

Weiss RE, Refetoff S. 甲状腺功能检查. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. 内分泌学:成人和儿童. 7日艾德. Philadelphia, PA: Elsevier Saunders; 2016:chap 78.