Why are Thyroid Tests Done and What Do Thyroid Levels Reveal?
What are Thyroid glands?
The thyroid gland is part of the body’s endocrine system. It is a butterfly-shaped gland located in the lower anterior part of the neck. Its main role in the body is to produce thyroid hormones for different functions including brain development, metabolism, and physical growth. Different thyroid tests can be done by taking a blood sample to check the adequacy of the thyroid gland in terms of hormone production. Blood test for thyroid can help determine if the thyroid function is normal, underactive, or overactive.
Should You Get a Thyroid Test Done?
Thyroid tests are usually done when there are clinical findings that suggest a condition affecting the thyroid. It is also done in cases of high risk patients who have a large chance of getting a thyroid disease. For hypothyroidism, some of the risk factors include female sex, over 60 years of age, family history of thyroid disease, autoimmune diseases, past hyperthyroidism, Down syndrome, and history of head or neck cancer. For hyperthyroidism, the risk factors include female sex, family history of thyroid disease, pregnancy, and smoking. It serves as a diagnostic tool for distinguishing between primary and secondary hypothyroidism and hyperthyroidism.
Thyroid stimulating hormone (TSH) levels are commonly measured to initially assess thyroid function. A normal TSH result means that the thyroid gland is functioning efficiently. High TSH levels indicate thyroid gland function failure and the thyroid condition called hypothyroidism may be the problem. Low TSH levels may also indicate a problem in the pituitary gland, a gland found in the brain that regulates function of the thyroid gland. In case low TSH is caused by the pituitary gland, this is also known as secondary hypothyroidism. In low TSH levels, the opposite happens and the thyroid gland is over-functioning and can be an indication of hyperthyroidism.
T4 or thyroxine is the main hormone produced by the thyroid glands. It is found in the blood in two different forms, namely as T4 and free T4 (FT4). Free T4 in the blood is considered to be more important when assessing thyroid function. FT4 levels in individuals with hyperthyroidism tend to be elevated while free T4 of patients with hypothyroidism will have low levels.
Combining the results of FT4 and TSH levels in the blood leads to a more accurate diagnosis of thyroid function. An elevated TSH and low FT4 levels are indicative of primary hypothyroidism wherein the thyroid gland is the main problem. In thyroid tests results showing low TSH and low FT4, it indicates a problem in the pituitary gland and is indicative of secondary hypothyroidism.
A thyroid test for T3 levels is most useful when trying to diagnose hyperthyroidism. It is also valuable when determining the severity of hyperthyroidism. T3 levels are usually the last test to produce abnormal results and have no value when trying to diagnose hypothyroidism. Patients with hyperthyroidism will have high T3 levels.
Thyroid Antibody Test
In patients with hyperthyroidism and hypothyroidism, the body sometimes produces antibodies against the thyroid which can either damage or stimulate it. Measuring the level of thyroid antibodies is useful in diagnosing the cause of the problem and can help determine if it is an autoimmune disease or not.
Radioactive Iodine Uptake Test
Radioactive iodine uptake (RAIU) test is a non-blood test used to determine thyroid gland function. T4 contains iodine and the thyroid gland utilizes a large amount of iodine from the blood in order to produce enough T4. Radioactivity allows the doctor to monitor iodine molecules in the blood. High RAIU levels are seen in patients with hyperthyroidism while low RAIU indicates hypothyroidism.
Hyperthyroidism vs. Hypothyroidism
Thyroid symptoms and thyroid treatment for hyperthyroidism and hypothyroidism are complete opposites. In hyperthyroidism, there is an overproduction of thyroid hormones while in hypothyroidism there is an underproduction of hormones. Symptoms of hyperthyroidism include frequent bowel movements, increased appetite, sweating, and weight loss while hypothyroid symptoms include constipation, sensitivity to cold, and weight gain. Thyroid treatment for hyperthyroidism involves the use of anti-thyroid drugs while hypothyroidism treatment involves intake of thyroid hormone medication.
Prompt treatment of a thyroid condition is important to avoid any complications. Thyroid tests are of great value in assessing the function of the thyroid gland and can help doctors make an accurate diagnosis of your condition.
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