So hormones. We all have them, all kinds of them. Today, I wanted to talk about the three thyroid hormones they test for when testing for hypothyroidism.


From the U.S. National Library of Medicine: TSH stands for thyroid stimulating hormone. A TSH test is a blood test that measures this hormone. The thyroid is a small, butterfly-shaped gland located near your throat. Your thyroid makes hormones that regulate the way your body uses energy. It also plays an important role in regulating your weight, body temperature, muscle strength, and even your mood. TSH is made in a gland in the brain called the pituitary. When thyroid levels in your body are low, the pituitary gland makes more TSH. When thyroid levels are high, the pituitary gland makes less TSH. TSH levels that are too high or too low can indicate your thyroid isn’t working correctly.

The standard range for TSH is 0.4 to 4.0 uIU/mL (ranges can differ slightly depending where you are tested).

TSH tells your thyroid what to do. If your thyroid is under producing, the pituitary gland will make more TSH to get your thyroid to make more hormone. If your thyroid is over producing, the pituitary gland will make less TSH.

High TSH indicates an underactive thyroid or hypothyroidism. Low TSH indicates an overactive thyroid or hyperthyroidism.


T4 or Thyroxine is the hormone produced by the thyroid.

From Healthline: Your thyroid produces a hormone called thyroxine, which is known as T4. This hormone plays a role in several of your body’s functions, including growth and metabolism. Some of your T4 exists as free T4. This means it hasn’t bonded to protein in your blood. This is the type available for use by your body and tissues. However, most of the T4 in your bloodstream is bonded to protein. Because T4 exists in two forms in your body, there are two kinds of T4 tests: a total T4 test and a free T4 test. A total T4 test measures the T4 that’s bonded to protein along with any free T4. A free T4 test measures only the free T4 in your blood. Because free T4 is what’s available to your body for use, a free T4 test is often preferred over a total T4 test.

The standard range for Free T4 is 0.8 to 1.8 ng/dL (ranges can differ slightly depending where you are tested).


From the Healthline: The thyroid produces a hormone called triiodothyronine, known as T3. It also produces a hormone called thyroxine, known as T4. Together, these hormones regulate your body’s temperature, metabolism, and heart rate. Most of the T3 in your body binds to protein. The T3 that doesn’t bind to protein is called free T3 and circulates unbound in your blood. The most common kind of T3 test, known as the T3 total test, measures both kinds of T3 in your blood.

The standard range for Free T3 is 2.6 – 4.8 pg/mL and the standard range for T3 Total is 60 to 180 ng/dL (ranges can differ slightly depending where you are tested).

So, those are the three hormones that are tested for when doing a thyroid function test, regardless of whether you have an underactive, overactive or normal functioning thyroid. These hormones will help your healthcare provider determine your thyroid function and if you may have or develop any kind of thyroid condition.

It’s important to know that ‘standard’ or ‘normal’ ranges can vary by test and and where you are tested (as I noted before), but it is also important to know that different health care providers and doctors can have varying opinions on what they consider low or high within the range. Everyone is different and will have a different optimal level for them, so make sure to work with a health care provider that you like and trust, and never be scared to get a second opinion.

*Disclaimer: I am not a medical professional. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your health care provider 

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