Once stimulated, the thyroid gland releases a particular type of thyroid hormone known as T4 (thyroxine), which is taken up by every cell in the body and converted to the more active thyroid hormone, T3. This hormone binds within the cell to increase metabolism.

We can measure both T4 and T3 with blood testing. However, the blood testing does not tell us what the concentration of thyroid hormone is inside the cells. It is the intracellular (inside the cell) binding of T3 that is necessary to provide the fuel the cell needs to function.

Unfortunately, we do not have a way to measure intracellular thyroid function. The blood tests are all indirect measurements of thyroid function.

In fact, there are conditions where the blood levels of thyroid hormones are adequate, yet a patient still suffers from many of the symptoms of hypothyroidism (thyroid deficiency).

Over the years, I have treated many patients who had normal thyroid blood tests, but responded positively when treated with small amounts of thyroid hormone.

During pregnancy, most doctors check a woman’s TSH and T4 levels. If these levels fall in the normal range, the patient is told that there is no thyroid problem.

But remember that no thyroid test can tell the whole story because thyroid hormone exerts its effects intracellularly. In addition, not checking a T3 level is absurd. You cannot diagnose a thyroid condition without a full thyroid panel, which includes testing for T3 levels.

The TSH range generally runs from about 0.5 to 5 mIU/L. After 20 years of examining tens of thousands of patients’ TSH tests, I can assure you that this range is much too wide.

The reference range for a laboratory test is calculated after hundreds of lab tests are drawn. Then the lab scientists perform a statistical analysis of the results to determine the range that 95 percent of the population tested falls into.

That means that 2.5 percent of the results will be abnormally high and 2.5 percent will be abnormally low.

This statistical manipulation only holds true if 95 percent of the population tested is in a normal, healthy range.

However, in the case of thyroid testing, I can assure you that 95 percent of the patients are not normal. A good portion of those patients actually have thyroid problems.

Laboratories do not screen healthy patients in order to set the reference ranges. Rather, they use all the lab tests available to them — that includes both healthy and sick patients.

But those who are going to the doctor and getting lab tests are generally sicker than a person who does not go to the doctor.

Therefore, the reference ranges are established using lab data from sick patients.

As I described in my book, Hypothyroidism: The Unsuspected Illness, laboratory tests can be a guide but they should not determine who does and does not have a thyroid problem.

Why? Because the TSH reference range (just like the T4 and T3 reference ranges) is much too large.

My experience has shown that the optimal TSH level for most patients is around 1.0 mIU/L.

When the TSH starts to get too high, it is a signal that the thyroid gland is starting to fail.

Studies have shown that elevated TSH levels within the reference range are associated with an increased weight gain.

In fact, for every 1 mIU/L increase in TSH within the reference range, women experience a five-pound weight gain1.

As a country, we are suffering from an obesity epidemic; two-thirds of Americans are either overweight or obese. I have no doubt that part of this problem is due to the misinterpretation of thyroid testing.

So, what can you do? If you see your TSH is increasing over time, don’t wait until you become ill. And if your doctor doesn’t want to work with you, find one that understands how to properly interpret thyroid tests.

A holistic healthcare practitioner will generally be more knowledgeable about this.