So your thyroid labs are "normal" but you feel like crap?
A common refrain I hear from clients is that they were convinced something was wrong with their thyroid until their physician told them their thyroid labs were normal. Yet they continued to suffer from a long list of debilitating symptoms: dry skin, weight gain, fatigue, a foggy brain, constipation, depression, joint pain, etc.
Though there are other possible causes for these symptoms unrelated to the thyroid, it’s often the case that these same clients have a thyroid dysfunction that has gone unidentified. How can that be when all the blood work is “normal”?
The thyroid gland is considered the master of metabolic function, controlling metabolism at the cellular level. Optimal thyroid function is critical for a multitude of physiological functions: body temperature, bone health, glucose and hormone metabolism, nutrient absorption and digestion, intestinal motility, liver function and detoxification, aging, cholesterol levels, and fat metabolism.
The thyroid gland is part of a larger system called the hypothalamus-pituitary-thyroid axis (HPT Axis). The hypothalamus - the control center for the autonomic nervous system, located in the brain - tells the thyroid to either increase or decrease metabolic function by sending a signal to the pituitary gland. The signal is a hormone called thyrotropin-releasing hormone (TRH) and the hypothalamus modulates the amount of TRH it sends to the pituitary based on the needs of the body. In response to “orders” from the hypothalamus, the pituitary gland sends its own hormone signal - thyroid stimulating hormone (TSH) - to the thyroid gland, telling it to either increase or decrease the production of thyroid hormone. When TSH rises, the thyroid “steps on the gas” and increases thyroid hormone production. When TSH falls, the thyroid gland “puts on the brakes”.
The thyroid gland produces two major types of thyroid hormone known as T4 and T3. The thyroid gland also releases T1, T2 and calcitonin but these hormones are not currently considered when evaluating thyroid function. T4 and T3 are released from the thyroid gland in a ratio of approximately 93% to 7%, respectively. T3 is considered the “active” form of thyroid hormone and is required by every cell in the body to drive cellular metabolism. T4, on the other hand, must be converted into T3 in order to be used by target cells and tissues. So, it’s really our T3 levels, and how well T3 is being utilized by our cells, that make the most difference in how we feel.
The conversion of T4 to T3 is a nuanced process and can be negatively impacted by a variety of factors. Because conversion occurs primarily in the liver and GI tract, adequate T3 production can be compromised by gut infections - parasites, bacteria, yeast and viruses - and anything that puts greater toxic burden on the liver. In addition to the T4 to T3 conversion, approximately 20% of T4 is converted into an inactive form of T3 called reverse T3 (rT3). As I’ve already mentioned, every cell in the body has receptors for thyroid hormone - bone cells, liver cells, brain cells, immune cells, mucosal barrier cells, etc. – but rT3 competes with Free T3 (fT3) at the cell receptor site, opposing the biological action of active T3 and slowing metabolism.
Since fT3 is the “accelerator” and rT3 the “brakes, they need to be in balance with one another. The fT3:rT3 ratio should be 20 or higher. Ratios less than 20, even in the context of adequate fT3 levels, results in a reduction of metabolic function. An online fT3:rT3 ratio calculator is available at: https://stopthethyroidmadness.com/rt3-ratio/
When Things Go Wrong
Hypothyroidism is far more common than hyperthyroidism and the signs and symptoms of both can overlap with those of other health disorders. But when things go wrong with the HPT axis, a cluster of correlating symptoms will eventually appear. Having said that, it’s quite common for adverse thyroid symptoms to be present long before blood markers shift outside the standard reference ranges used by most conventional laboratories.
Sensitivity to cold
Irregular menstrual periods
Joint and muscle pain
Shortness of breath
Irregular menstrual periods
Testing Your Thyroid
Thyroid function is evaluated via a simple blood test but most physicians order preliminary screenings only. There are several “thyroid markers” that should be part of thyroid testing, but conventional medicine typically focuses on just a few. This can lead to misdiagnosis, under-diagnosis and improper management. If your doctor has tested your thyroid function, they may have measured your TSH, fT3 and fT4. It’s also quite possible that they only measured your TSH levels and called it good.
In my opinion, the most critical thyroid markers to evaluate are:
Thyroxine binding globulin
TgAb or TGB antibodies
To learn more about these markers and more, review the table below:
Note: Studies suggest that anywhere from 11-35% of people with thyroid autoimmunity may never test positive for thyroid antibodies
Since doctors often evaluate thyroid function by screening TSH only, if TSH appears “normal” additional thyroid markers may never be evaluated regardless of symptoms. Even a conventional “complete thyroid panel” (TSH, fT4, fT3) fails to provide enough information to identify certain patterns of thyroid dysfunction. To further complicate matters, the typical (standard) reference ranges for thyroid markers are too liberal and can lead to under-diagnosis. Standard reference ranges reflect levels of thyroid markers that are common among the general population – a significant percentage of which may have clinical and sub-clinical thyroid dysfunction. Functional reference ranges, on the other hand, are narrower and can more accurately reflect optimal thyroid function in healthy individuals.
Note: Standard reference ranges vary from lab to lab. Functional reference ranges can vary from practitioner to practitioner.
If we just compare the standard vs. functional ranges for TSH, fT3 and fT4 (the most common markers that conventional practitioners evaluate), it’s easy to see why thyroid dysfunction is frequently missed (particularly cases of hypothyroidism). To a conventional practitioner a fT4 of 1.0, a fT3 of 2.8 and a TSH of 3.5 are well within normal limits. To a functional practitioner such results indicate hypo-function of the thyroid and, more importantly, that underlying causal factors are likely present. Unlike standard medical treatments that focus almost exclusively on the thyroid gland, functional practitioners use comprehensive investigative strategies to resolve the underlying causes of your thyroid disorder.
Even when thyroid dysfunction IS diagnosed by conventional practitioners, the underlying causal factors often go unaddressed. Thyroid dysfunction doesn’t occur in a vacuum and simply prescribing thyroid hormone replacement may not alleviate symptoms. The hypothalamus-pituitary-thyroid axis is vulnerable to many environmental and physiological influences - most commonly heavy metal toxicity, autoimmunity, gluten sensitivity, nutrient deficiencies, chronic viral infections and parasite, bacterial and fungal infections. Such health issues must be resolved to restore thyroid function.
If you want a comprehensive assessment of thyroid function and are interested in investigating the root causes of imbalance, I recommend seeking out a functional practitioner.