Hypothyroidism and Hashimoto’s Disease are common yet under diagnosed conditions. When the thyroid gland produces insufficient thyroid hormones, your metabolism slows down, and this can upset the normal chemical balance of your entire body.

While there are usually no symptoms in the early stages of hypothyroidism, various symptoms—including unexplained and gradual fatigue, weight gain, muscle cramps, memory and hair loss—may start to show as the disease progresses. These symptoms are not the basis of a definitive diagnosis of hypothyroidism because they are also associated with other diseases, like diabetes. Thyroid function tests were initially developed in order to measure how well the thyroid gland is working. However, the parameters used to interpret thyroid lab results often lead to an incorrect diagnosis.

For example, if you present unexplained symptoms of hypothyroidism, your doctor may order a limited thyroid test to check your hormone levels.  This test usually checks Thyroid Stimulating Hormone (TSH), triiodothyronine (T3), and T4. If your test results indicate a thyroid hormone imbalance, your doctor may prescribe you synthetic thyroid hormone therapy. On the other hand, if your tests come back within a “normal” range, you may be assured everything is fine and perhaps even receive symptoms-relieving medications for your condition. However helpful it may be to do these tests, this is ultimately an inefficient and ineffective way to treat thyroid issues, and may not catch them, especially in their less severe, beginning stages.

How Normal is your “Normal” Result?

​You are more in touch with your body than anyone else.  You know how and what you feel, even when a clear cause doesn’t show up on a standard lab test. Doctors use reference ranges to determine if your result falls within predetermined “normal” values. Unfortunately, the thyroid tests used by labs are not always helpful because the population on which these tests are based is not representative of a truly healthy, thyroid-balanced population.

The average person getting a thyroid test is likely to have health challenges already, and may already have a known or undiagnosed thyroid condition. Conventional “normal” ranges are flawed because the statistical average from these test populations does not take into account the pre-existing imbalances that may or may not be present in the sample group. In this context, a normal lab result, simply means that you are as normal as other people who are also likely to have thyroid problems. Functional medicine takes a different approach and looks at a narrower range of normal in order to compare your results with that of a healthy population. 

How Your Thyroid Gland Works

Your pituitary gland secretes TSH in response to signals from your hypothalamus. The TSH then stimulates the production and release of T4 and a small amount of T3 from your thyroid gland. T4 is the storage form of thyroid hormone and must be converted to T3, the active form, before it can influence bodily metabolic functions. T3 can exist as “free T3,” the active form absorbed by various cells in the body, or as “reverse T3,” the non-active hormone.

What's Different About Functional Medicine?

When your doctor asks for a thyroid lab test, it usually checks only the levels of your TSH. In some cases, T4 may also be requested. However, your thyroid health is much more than TSH and T4. In fact, TSH indicates the level of your pituitary function rather than thyroid function.

Much more useful information can be found by checking other key components of your thyroid system.  For this reason, in functional medicine more tests are performed in addition to comparing your lab result with an “optimal” range instead of clinical “normal” values in the process of determining imbalances.

What Tests Do You Need to Determine Your Thyroid Health?

​TSH
A high TSH level indicates your hypothalamus is causing your pituitary gland to work harder than it needs to; it is a sign of low thyroid production. A low TSH level, on the other hand, indicates hyperthyroidism or excessive thyroid hormone (T3) supplementation.

What if your TSH is “normal”?

A “normal” TSH does not necessarily mean your thyroid is healthy. It is more useful to determine whether or not your TSH levels are in the optimal range, especially when symptoms persist. In fact, a study showed that even with a “normal” TSH of 2.5-3.5 mlU/L, patients still had a 69% risk of developing a heart attack or stroke.

Reference range: .40-4.5 mlU/L
Optimal range: 1.8-2.5 mlU/L

Total T4
T4 is the storage form of the thyroid hormone and consists of both the free, potentially useful form, and the bounded form. Unless measured in conjunction with T3 uptake, total T4 levels don’t give a clear picture of overall T4 activity.

Reference range: 4.5-12 mcg/DL
Optimal range: 6.0-11.9 mcg/DL

Free T4​
Free T4 levels indicate the amount of active T4 in your body, and a low value of free T4 indicates hypothyroidism. This reading may show up as normal even in the sub-clinical and early stages of thyroid disease. 

Reference range: 0.8-1.8 ng/DL
Optimal range: 1.0-1.5 ng/DL

T3 Uptake​
The T3 uptake test is used to indirectly measure the activities of other hormones, like estrogen and testosterone, and to measure their binding behavior compared to thyroid hormones. 

Reference range: 22-37 %
Optimal range: 27-37 % 

Total T3​
Total T3 levels indicate the amount of active thyroid hormones in your body.  Total T3 levels are a good measure of your body’s ability to convert T4 to T3 and can be used to rule out hyperthyroidism. 

Reference range: 76-181 ng/dL
Optimal range: 90-168 ng/DL

Free T3
Free T3 (FT3) are the active and functional form of thyroid hormones. Low T3 indicates your body is not converting enough T4 into free T3 adequately, a very common cause of hypothyroidism. Low FT3 is also associated with an increased risk of heart failure. 

Reference range: 2.3-4.2 pg/mL
Optimal range: 2.8-3.5 pg/mL

Reverse T3
Reverse T3 (RT3) is unusable for thyroid hormone functions, and it slows down your metabolic process by competing with free T3. A high RT3 indicates the rate of T4 to T3 conversion is high while FT3 is low. Chronic stress and mercury toxicity are connected to increased reverse T3 levels in some reports.

Reference range: 8-25 ng/DL
Optimal range: 10-25 ng/DL

Thyroid Antibodies

​Thyroid conditions are mostly autoimmune in origin and result from your body’s immune system fighting your own thyroid gland. A high level of thyroid antibodies may indicate an ongoing autoimmune attack. Over 90% of hypothyroidism is caused by an autoimmune reaction. When this occurs, the condition is known as Hashimoto’s disease. Hyperthyroidism due to an autoimmune reaction, on the other hand, is termed Grave’s disease.

There are two types of thyroid antibodies: Thyroid peroxidase antibodies (TPO) and Thyroglobulin antibodies. Both of these antibodies are found in elevated numbers in autoimmune spectrum diseases such as Hashimoto’s, and they are important indicators that a case of hypothyroidism may have an autoimmune origin.

Thyroid Peroxidase (TPO) Ab optimal range: 0-6.8 IU/mL
Thyroglobulin Ab optimal range: 0-0.9 IU/mL