Thyroid Stimulating Hormone Blood Test: Description & Optimal Ranges

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  • 0:01 Thyroid-Stimulating…
  • 1:01 Thyroid Gland Hormones
  • 2:04 Uses
  • 2:41 Results
  • 3:43 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

The thyroid-stimulating hormone blood test is an effective way to evaluate the function of the thyroid gland. It can be used to diagnose thyroid conditions like hypothyroidism and hyperthyroidism. Learn about the test and what the results mean.

Thyroid-Stimulating Hormone Test

Here's a medical riddle for you to solve. This woman visits the doctor complaining of weight gain, fatigue, and constipation. This man visits the doctor complaining of weight loss, difficulty sleeping, and diarrhea. The two people present with the exact opposite symptoms, yet the doctor was able to diagnose both patients using the same blood test. Can you guess what test the doctor ordered?

If you guessed the thyroid-stimulating hormone test, which is the screening test used to evaluate thyroid function, then you are correct. The thyroid-stimulating hormone test, or TSH test for short, can be used to diagnose thyroid conditions like hypothyroidism, which is what our female patient suffers from, or hyperthyroidism, which is the condition plaguing our male patient. In this lesson, we will take a closer look at this blood test and how the test results are interpreted.

Thyroid Gland Hormones

Before you learn more about the test, it will be good to refresh your memory about the thyroid gland and the hormones associated with it. You might recall that the thyroid-stimulating hormone, abbreviated TSH, is produced by the pituitary gland in response to signals from the hypothalamus.

This sequence of events is a type of feedback loop that ensures the thyroid produces the proper amount of thyroid hormones. For example, if there are too many thyroid hormones circulating in your bloodstream, then the pituitary gland stops secreting TSH, and vice versa. Thyroid-stimulating hormone's job is described by its name; in other words, TSH stimulates the thyroid gland to produce its own hormones. The hormones from the thyroid are T3, or triiodothyronine, and T4, also known as thyroxine. Together, these hormones help control the body's metabolic rate.


The thyroid-stimulating hormone blood test has a number of uses. As we already mentioned, the TSH test is used to diagnose hypothyroidism and hyperthyroidism. It can also be ordered at regular intervals to evaluate the thyroid function in a person with a known thyroid condition. This regular testing is an effective way to monitor and adjust medication levels. We often see that routine TSH screenings are performed on babies to check for an underactive thyroid in a newborn. And TSH testing can be used to help diagnose infertility problems in a woman who is having trouble getting pregnant.

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