The symptoms of thyroid disease range from weight gain, cardiovascular issues, constipation, and depression to weight loss, anxiety, insomnia, and tremors. A relatively simple blood test can be prescribed by a physician to test whether the thyroid is overactive or underactive.
Thyroid hormones are released throughout the body and they have a significant impact on health and mental well-being. The main hormones are thyroxine (T4) which contains four iodine atoms. T4 is converted by the thyroid into triiodothyronine (T3). Understanding the information thyroid blood tests provide can improve the dialogue between doctors and patients and help to ensure the best treatment results.
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Thyroid blood tests measure a number of thyroid functions. One hormone that is tested is called thyroid stimulating hormone (TSH) which is made in the pituitary gland and has a direct relationship with the thyroid. TSH controls how much T4 the thyroid produces which then affects the production of T3.
According to the American Thyroid Association
, "The amount of TSH that the pituitary sends into the blood stream depends on the amount of T4 that the pituitary sees. If the pituitary sees very little T4, then it produces more TSH to tell the thyroid gland to produce more T4. Once the T4 in the blood stream goes above a certain level, the pituitary’s production of TSH is shut off."
The THS test is often the first test
a physician will order to check thyroid health and a below normal level generally indicates hyperthyroidism which is an overactive thyroid while an "abnormally high TSH level suggests hypothyroidism" which is an underactive thyroid.
A T4 test is also one of the first blood tests used to measure thyroid health
. There are two types of this test, one measures T4 and the other measures free T4. Free T4 is distinguished because it is not bonded to protein in the blood. There is a direct relationship between the pituitary TSH and T4. For example, a low T4 and a low TSH might indicate the pituitary gland is not functioning properly as the pituitary normally releases TSH to stimulate T4. A high TSH and a low T4 points to an issue with the thyroid gland.
The T3 test looks at the amount of T3 in the blood, either attached to proteins or free. According to the National Institutes of Health
, a higher than normal level of T3 may indicate hyperthyroidism while a lower level of T3 can indicate hypothyroidism. Pregnancy and certain medications such as birth control pills and steroids can affect T3 test results.
Although the TSH, T4, and T3 tests are the most common ways for physicians to assess thyroid health, the results do not always present a clear picture of the thyroid's performance as it relates to health symptoms experienced by the patient. An additional test
is a thyroid antibody test that may help diagnose Hashimoto's thyroiditis, a disease in which the immune system attacks the thyroid. Yet another test is a radioactive iodine uptake test, which involves swallowing a small amount of iodine and having it tracked by a physician to measure thyroid performance.
This article is for information only and is not intended as medical advice. Talk with your doctor about your specific health and medical needs.
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