Welcome to our guide on thyroid stimulating hormone (TSH), the blood test doctors order most often to check if the thyroid gland is functioning normally. A TSH level indicates whether you are making or taking the right amount of thyroid hormone.
Thyroid stimulating hormone is made by the pituitary gland in the brain and is released into the blood stream. When TSH reaches the thyroid gland, it stimulates the gland to produce more thyroid hormone.
When the blood level of thyroid hormone drops below normal, the TSH level rises. When there is too much thyroid hormone, the TSH level gets very low. So, an abnormally high TSH level almost always indicates an underactive thyroid gland. A very low TSH level usually means there is too much thyroid hormone in the blood. There are some rare causes of an underactive thyroid gland with a low TSH. We'll get to that later.
Let's get started.
What is your TSH test result?
Source: from Harvard Health Decision Guides, Harvard Health Publications, Copyright © August 2010 by President and Fellows of Harvard College. All rights reserved. Used with permission of StayWell.