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What is a thyroid stimulating hormone level test?

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Quick Answer

A thyroid stimulating hormone test is a procedure that measures the amount of thyroid stimulating hormone in an individual's blood, according to Healthline. A health care professional performs this test by drawing blood from the patient's vein and sending the sample to a laboratory for analysis.

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Full Answer

Doctors may order a thyroid stimulating hormone test to investigate symptoms of an overactive or underactive thyroid gland or to monitor treatment of these conditions. The hormone levels can vary throughout the day, and it is best to conduct the test in the early morning hours, says the National Institutes of Health.

Normal values may vary slightly depending on the laboratory but generally range from 0.4 to 4.0 milli-international units per liter. While normal ranges are generally desirable, there are instances where other values are more appropriate, according to the National Institutes of Health. For example, lower values may be preferable for patients who have a pituitary disorder or thyroid cancer.

Higher-than-normal thyroid stimulating hormone levels are usually indicative of an underactive thyroid gland, potential causes of which include thyroiditis, congenital defects, radiation treatments, and use of medications such as lithium and amiodarone, states the National Institutes of Health. Lower-than-normal thyroid stimulating hormone levels may be a sign of an overactive thyroid gland, potential causes of which include Graves disease, toxic nodular goiter, excessive iodine in the body, and use of medications such as steroids, dopamine and morphine.

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