Hypothyroidism

Lesson 4: Getting Your Diagnosis

Thyroid Testing: What to ask for

Getting your thyroid tested properly takes a little bit of patience, some knowledge and a lot of effort, in some cases. Tests are usually needed to determine whether you are hypothyroid or not. If a diagnosis is what you seek, and it is if you require treatment, then you need to become familiar with not only the various thyroid tests but also their interpretation. In other words, you need to know what test to ask for and how to understand what your results mean for you.

To get to the test, you must have convinced your doctor by your symptoms, your family history or a combination of the two, that you are indeed hypothyroid. Most doctors won’t (or can’t due to insurance or other restrictions) order a thyroid test unless there is reason to suspect that you have a thyroid condition.

So, if you are at the point of testing, congratulations! You’ve passed several hurdles and may be well on your way to a diagnosis and eventual treatment. Sounds like smooth sailing, right?

That would be a big negatory!

Currently, there is what some refer to as “the tyranny of the TSH.” (See Living Well With Hypothyroidism pp 87 – 90 for more information.) Basically, that means that most doctors use the TSH test exclusively to determine the health and fitness of the thyroid.

TSH, or thyroid stimulating hormone, is a product of the pituitary gland. When there is not enough thyroid hormone in the body, it tells the thyroid to produce more. It is a very sensitive hormone. However, it works counter-intuitively to hypothyroidism. What I mean is that if your TSH level is too high, then you are probably hypothyroid.

Remember: If TSH is too high, then you are probably hypothyroid. If TSH is too low, then you are probably hyperthyroid.

So, what’s a normal TSH level?

That can vary from lab to lab. Most endocrinologists believe that a normal TSH lies within the 0.3 to 3.0 level. (Prior to 2003, it was 0.5 to 5.5.) Therefore, you may want to ask your doctor what the lab or clinic he or she uses determines as low or high TSH levels. It could make a difference in your diagnosis, or lack thereof.

Now, if your TSH is considered normal and you still have symptoms, you may want to push the envelope a bit and try for another test. TSH doesn’t always tell the whole story, despite what the medical party line says. Most of the time, two different tests are needed to diagnose low thyroid function, so don’t be afraid to ask for another one.

Of course, it may not be easy to get your doctor to agree to more tests. Just make your case logically and try to be consistent with what you ask for. If all else fails, make a note of your doctor’s refusal to test, have him or her sign it and put it in your medical file.

If that doesn’t get him or her to perform other tests, well, then you just may decide to find another doctor.

I know that’s an extreme situation. Besides, we don’t even know what the other tests do yet, do we? So, before we fire our doctors, why don’t we learn a little more about thyroid testing so we know what to ask for and how to ask for it.

T4, called thyroxine, is one of the hormones produced by the thyroid itself. It gets released into the bloodstream and helps control the body’s metabolism by converting oxygen and calories into energy. Most of the T4 in the blood is bound to proteins, usually called TBGs, or thyroxine binding globulins. The remainder of T4 (usually about 1 – 4% in total) acts on the body’s cells.

The T4 test measures the amount of T4 hormone in the blood. There are two types of T4 tests. One is the Total T4, or Serum Thyroxine. Just as its name suggests, this test measures the total amount of thyroxine in the blood. Lower than normal levels of thyroxine along with an elevated TSH indicate hypothyroidism. The range is generally between 4.5 – 12.5.

The second T4 test is called Free T4. It refers to that 1 – 4% of T4 that does not bind with the TBGs. A result of less than 0.7 can indicate potential hypothyroidism.

T3, or triiodothyronine, is the second hormone produced by the thyroid. Although the body produces more T4, T3 is the more active of the two thyroid hormones. Certain conditions such as pregnancy can increase the level of the TBGs which carry T3 and may artificially raise the level of the total T3. In that case, the free T3 test may need to be run. Since less than 1% of T3 is free, this test can be very sensitive.

If your test results are low for the T3 or Free T3 test, it may indicate hypothyroidism. T3 is considered normal in the 80 to 220 range whereas Free T3 is normal from 2.3 to 4.2.

Usually, by this point, your physician will be able to make a diagnosis of hypothyroidism. If not, you have two other options. They are more difficult to make a case for, but all things are possible with patience, persistence and knowledge. (At least, I am pretty sure they are!)

The first of these is the TRH test. Usually, the TRH test is not run unless your doctor suspects that you have a condition referred to as secondary hypothyroidism. Secondary hypothyroidism is lower than normal circulation of thyroid hormones that is caused by damage to the hypothalamus or pituitary gland. In other words, the thyroid hormones aren’t being regulated properly because the stimulating mechanisms in the brain aren’t functioning well enough.

In the TRH test, the patient is given an injection of TSH. The patient’s responses to the TSH are monitored and the results determine whether the patient’s thyroid dysfunction occurs in the hypothalamus or the pituitary gland.

This test is rarely used for primary hypothyroidism because the TSH test is a better indicator than the TRH for that condition.

The only other option used to be a Thyroid Scan. This test required that you take radioactive iodine. Your thyroid would then go through an imaging process sort of like an MRI and, based upon the view, you’d know if you had a goiter, or nodules. Usually, this test was better for determining thyroid cancer and whether the nodules (thyroid lumps) were hot (malignant) or cold (benign).

Nowadays, you can get a thyroid ultrasound. There’s no radiation and the imaging is pretty sensitive. It can determine the existence and size of a goiter and certain masses, including nodules and/or cancer, in the thyroid. This procedure, along with other diagnostics, may just get you closer to a diagnosis.

As you can see, it’s not always easy to test the thyroid. Even when you do, the results are not completely conclusive. The thyroid is difficult to understand and even harder to diagnose sometimes.

However, now that you know what and when to ask for certain thyroid tests, you have crossed another potential barrier in coping with hypothyroidism.

In the next section, we’ll discuss what happens when you still feel hypothyroid despite normal results. There’s a condition called subclinical hypothyroidism. Millions have it.

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