The TSH Story

What's the deal about TSH?

TSH. Try Something Harder. It can feel like you always have to do that when your thyroid isn't working right, but TSH stands for Thyroid Stimulating Hormone. The TSH test is the main one that doctors use to diagnose hypothyroidism or hyperthyroidism, so it's an important test to understand.

TSH is a pituitary hormone, not a thyroid hormone. Its job is to stimulate the thyroid to produce more thyroid hormone, so a high TSH level usually indicates that your body isn't getting enough thyroid hormone. This condition is hypothyroidism. A too-low TSH level usually indicates the opposite, or hyperthyroidism.

The main problem with the TSH test is that the reference range for it is too wide at most labs. The upper end of the range at some labs goes as high as 6, but according to the hundreds of references that we've compiled, symptoms of hypothyroidism accompanied by a TSH level over 2, sometimes lower, are suspect. Whenever you get lab tests, ask for a copy of the results. Don't just let someone tell you that your TSH level is "normal."

Another problem with going by TSH levels is that because TSH is a pituitary hormone, sometimes it doesn't tell the thyroid story. If there's a problem with the pituitary gland, or the hypothalamus (which controls the pituitary), TSH could be at an optimal level, but your actual thyroid hormones (T4 and T3) could be too low, or too high. Using the TSH test to check for thyroid problems in this situation is like looking at the thermostat to check the temperature of a house when the thermostat itself is broken.

What now?

If you have a "normal" TSH level but you still think you have hypothyroidism, ask for more thyroid testing, such as free T4 and free T3 tests, and tests for thyroid antibodies. A TRH stimulation test might produce more conclusive test results. Note that hypERthyroidism can also be missed by relying too much on the TSH test; some people get symptoms of hyperthyroidism when their TSH level is within the lab reference range, but at the low end of the range. You can also print our files of references about TSH to bring to your doctor. If you think you are undertreated, you can use these compilations to ask your doctor about a dose increase.

To learn more about TSH levels and undertreated hypothyroidism, see Help, I'm Hypothyroid and I Still Don't Feel Well by Mary Shomon.

Keep in mind that some other health conditions have symptoms that are similar to those of a malfunctioning thyroid. For more on this, see Maybe It Isn't Your Thyroid in our Archives section.

What about low or suppressed TSH levels?

A lot of hypothyroid patients need to have a very low TSH level to be symptom-free.

Some doctors believe that too little thyroid medication is preferable to the possibility of temporarily overdosing, and won't increase the dose once the TSH level is within the wide reference range. While it's commonly taught that too much thyroid hormone causes health and functioning problems, it's not as well known that so does even a slight deficiency of thyroid hormone. Undermedicating a patient is like stopping a diet too soon, or driving a car too slowly for traffic conditions. Doctors generally don't advise patients on diets to lose only some of their excess weight so that they don't lose too much. Neither do they drive under the speed limit so that they don't risk driving over it by accident.

If you take a little too much thyroid medication, you can reduce your dose and still reach your target. You'll never get there, however, if you don't have enough thyroid hormone. Cars have speedometers, which are usually reliable, but the TSH test has been proven to be an unreliable indicator of adequate thyroid hormone levels.

Medical journal articles have shown that treatment started with a TSH level in range accompanied by hypothyroidism symptoms resulted in health improvements. In addition, a TSH level at the higher end of the range (but within many reference ranges) may correlate with other health conditions — depression, heart disease, and high cholesterol, for example.

Where are those TSH references?

See the links at the right on this and every page in the TSH section of this site. The TSH References page provides an overview of the references and why we need them. The compilations of references are divided into medical journal references and references from other sources, and each has a printer-friendly version so that you can take these references to your doctor if they're relevant to your situation. On the "TSH: Patients' Experiences" pages, you can read how getting the TSH level at the optimal level greatly improved the lives of many thyroid patients.

On our Suppressed TSH Levels: Medical Journals page, we have medical references to counter doctors' concern about a suppressed TSH level with some of their patients.

T3 levels may be another piece of the puzzle to feeling well. See also our T3 Supplementation article and links.

Lois Summers