TSH Test FAQ
Why would I get a TSH Test?
What is TSH?
What does an abnormal TSH Test level mean?
What type of specimen will I submit?
Do I need to fast to take this test?
How long does it take to get test results?
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Related To The TSH Test
More About the TSH Blood Test
The TSH test, also known as thyroid-stimulating hormone test or TSH lab test, measures the TSH blood level.
TSH is a hormone produced by the cells known as thyrotrope cells in the anterior part of the pituitary gland. The thyroid gland produces several important hormones, including T3 (triiodothyronine) and T4 (thyroxine) and TSH serves to regulate the activity of the thyroid gland and the hormones it produces. TSH primarily works on special receptors found on follicular cells of the thyroid gland to regulate it. TSH is quickly metabolized in the blood within hours.
The body has intricate feedback mechanisms that alert the pituitary when the body needs more or less thyroid activity. When the pituitary gets a signal that the body needs more thyroid activity, it releases more TSH which sends a signal to the thyroid gland that tells it to increase the production of thyroid hormone. If the pituitary gets a signal that the body needs less thyroid activity, it decreases its production of TSH in an effort to reduce the overall activity of the thyroid gland.
An understanding of how the thyroid works is helpful in making sense of what an abnormal TSH level means. When the TSH blood test level is high, this suggests that excessive TSH is being produced in an attempt to stimulate the thyroid gland. This frequently happens because the pituitary gland is getting a signal from the body that it needs more thyroid hormone. As a result, a high TSH level suggests that one has an underactive thyroid (i.e. low thyroid activity or hypothyroidsim) which can typically be better assessed with a more comprehensive hypothyroidism test panel.
Conversely, a low TSH level suggests that the thyroid might be overactive (i.e. high thyroid activity or hyperthyroidism). In this situation, the pituitary gland is receiving feedback from the body that the thyroid is too active and, as a result, needs less stimulation. To reduce thyroid stimulation, the pituitary gland cuts back on the production of TSH with the intention of reducing the production of thyroid hormone by the thyroid gland. While a TSH test result can help screen for an overactive thyroid, more detailed investigation of high thyroid gland activity can be done with the hyperthyroidism test panel.
Getting a TSH test near you should be relatively straightforward as the TSH blood test is a common lab test and every standard Quest Diagnostics lab location should have the equipment needed to perform it. On the day of your test, a small amount of your blood will be drawn into a vial and the specimen will be run in a machine. TSH lab results come back relatively quickly and a reference range will be provided on the lab report against which you can compare your results. On the TSH sample lab report provided above, the TSH test result reported is 0.03 mIU/L which is considered low when compared against the provided normal range of 0.40-4.50 mIU/L. Low TSH levels in this case might indicated hyperthyroidism and should be interpreted in the context of clinical symptoms and possibly with more advanced thyroid lab tests.
As a result, the measured level of TSH using the TSH blood test is useful because it serves as an indicator as to whether the thyroid gland is doing its job. Because it gives a snapshot of the overall health of the thyroid gland, the TSH test is frequently used as an initial screening test for overall thyroid health. Normally, TSH levels will vary throughout the day as the body turns on and off processes in connections with its daily cycles. As with most lab tests, measuring one's TSH levels over time is helpful because it can help identify abnormal trends that are specific to one's body.
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