Your Basic Thyroid Test May Not Be Enough

Marie Parks

Moody, tired, or gaining weight? It could be your thyroid.

Of course there are many underlying factors that could contribute to these frustrating
symptoms such as hormones, stress, neurotransmitter imbalance, etc. However, the prevailing culprit, your thyroid, is often left undiagnosed.

Thyroid malfunction is a common cause of these symptoms and is not even considered by many doctors. To make matters worse, the doctors who are aware of the role thyroid can play usually do not sufficiently assess the lab values that are needed to get a complete picture, and this results in the person not being treated properly.

About 50% of the people suffering thyroid malfunction remain undiagnosed, which can increase the risk of other health issues such as cardiovascular disease, osteoporosis, and infertility!

Your Thyroid in a Nutshell

The thyroid works by a negative feedback loop with the hypothalamus and the pituitary gland. The hypothalamus tells the pituitary gland to release TSH (thyroid stimulating hormone) which then tells the thyroid to release T4 (thyroxine) and T3 (triiodothyronine).

In the body, T4 is converted into T3, which is the active form and the one that is more directly involved in metabolism. If your T4 is not efficiently converting into T3, you may feel weak, tired, and depressed. However, figuring out how to address these symptoms is not an easy task.

How and Why “Thyroid Testing” Fails You

As a health advisor for five years, some of the most common ailments that people complained about were unexplained weight gain, lethargy, lack of motivation, and brain fog. When I would question them as to whether they’ve had their thyroid tested, (if the answer was yes) it was not surprising to hear that their doctor tested it and it was fine.

Probing further, the test they usually were referring to was TSH by itself. The problem with this is that a person can have a TSH level in range, but low levels of T4 and T3. To make things even more complicated, even testing for TSH, T4, and T3 may not be enough information for a complete picture!

Not all T4 is available to convert into T3 because some of it is bound to proteins. Similarly, some of your T3 is also bound to proteins. About 99% of circulating thyroid hormones are bound to carrier proteins, making them metabolically inactive.1

When you have your T3 levels measured, it’s a combination of both the bound and the free T3. Your free T3 is the amount that is available for tissues. Therefore, knowing your free T4 and free T3 levels can help diagnose thyroid function.

Together with TSH, T3, T4, free T4, and free T3, testing for another hormone, called reverse T3, can help complete the picture of one’s thyroid health. Reverse T3 is a nonfunctioning form of T3 that is produced by the conversion of T4. Reverse T3 is not only inactive, but it also blocks thyroid receptors, hindering the action of regular T3.2 The conversion of T4 to T3 is hampered by cortisol, which is secreted by the adrenal glands when under prolonged stress.

Did You Know About the Antibodies?

Another key in assessing thyroid function is measuring the thyroid antibodies TPO (thyroid peroxidase antibody) and ATA (antithyroglobulin antibody). These antibodies are elevated in autoimmune diseases such as Hashimoto’s and Graves’ disease.

In such cases, the body’s own immune system attacks the thyroid, lessening its ability to make hormones, and causing symptoms of underactive (and sometimes overactive) thyroid. It is crucial to know if one’s symptoms are due to an autoimmune issue because the potential suggestions can be contraindicated.

Your Medication Might be Doing More Harm than Good

It’s common for a doctor to prescribe Synthroid or Levoxyl for someone whose test results show elevated TSH (remember, this is a negative feedback loop, so high TSH is indicative of hypothyroidism). These medications are just T4, and if someone is not converting it to T3, they are still going to exhibit undesirable symptoms.

There are other medications that can be prescribed as alternatives such as Nature-throid, Armour thyroid, and Westhroid which provide T4 and T3. Another option is Cytomel, which is the synthetic form of T3.

This is why comprehensive testing is important even for those who are already taking medications.

The Bottom Line

If you are gaining weight, tired, losing hair, and in a slump, your thyroid could be the reason. Assessing thyroid function can be complicated, so it is best to make sure your test looks at all aspects.

Comprehensive testing can help to diagnose the cause of your problem, so that you can be happy and healthy once again!


  1. Nussey S, Whitehead S. Endocrinology: An Integrated Approach. Oxford: BIOS Scientific Publishers; 2001. Box 3.28. Available at:
  2. Acta Med Austriaca. 1996;23(1-2):17-30.


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