Low Thyroid Function - Testing Beyond TSH

Experiencing vague symptoms such as unexplained weight gain, hair loss, fatigue, constipation, or mood swings can be frustrating. Many of us with symptoms such as these simply brush them off and attribute them to daily life stresses. Others seek answers only to be told that their symptoms are “all in their head” or “a normal part of aging” and that “nothing can be done”. Over time, we settle for a health status which becomes normal for us, albeit not optimal.

For 10 years, I experienced many of these same vague symptoms, and more, before I was ultimately diagnosed with hypothyroidism. My search for answers led me to naturopathic medicine and solidified for me how just how important hormones are to our overall health. As a result, I particularly enjoy identifying and treating conditions resulting from hormone imbalances.

Hormones are the master regulators of our body, and this is especially true for thyroid hormones. Every cell in the body needs thyroid hormone. We need it for our most basic and fundamental physiology, and it is essentially the basis for our basal metabolic rate. A lack of thyroid hormones leads a gradual decline in energy, mental function, gut motility, and mood. With low thyroid hormones, one may also experience cold intolerance, weight gain, fatigue, constipation, and dry skin, hair, and nails. Sometimes these symptoms can be mild and vague and go undetected for years.

According to the American Thyroid Association, approximately 20 million Americans have some form of thyroid disease and more than half of these are unaware of their condition. Women are particularly at risk – one in eight women will develop a thyroid disorder during their lifetime, and they are 5 to 8 times more likely than men to have a poorly functioning thyroid.

Identifying a problem with your thyroid can be tricky, and it’s important to understand the intricacies of testing for low thyroid function and knowing why “normal” results on a single test may not be giving you the whole picture.

What is TSH?

The most recognized test in the conventional medical world to access thyroid function is TSH, which stands for Thyroid Stimulating Hormone. With 12% of the US population developing a thyroid condition in their lifetime, it is certain that at some point you will have this test completed as routine part of your annual physical.

Made specifically in the pituitary gland of the brain, TSH is a signal from the brain to the thyroid gland telling it to produce more (or less) thyroid hormone. What it is not is a direct measurement of your thyroid hormones. Depending on where your TSH falls in a very wide reference range, a doctor may make assumptions about your thyroid gland function and/or make changes in your thyroid medication dosing.

TSH functions based on a feedback loop. A lower TSH generally means there is more hormone in the system, and thus there is less need to tell the thyroid gland to produce thyroid hormone. A higher TSH is the opposite – a higher TSH indicates that the body does not have enough circulating hormone, and thus there is more need to tell the thyroid gland to produce thyroid hormone.

Shortcomings of TSH Lab Results

“Normal” reference ranges for TSH can be as wide as 0.5 - 5 uIU/mL and sometimes up to 8. The problem with this wide reference range is multifactorial. First, what’s considered a “normal” range of TSH for healthy people includes elderly patients and those with borderline low thyroid disease state called subclinical hypothyroidism. Inclusion of these patients leads to an overly wide reference range, and as a result, most conventional physicians may miss an elevated TSH level. Subsequently, people are told that their thyroid tests are “normal” when they are clearly presenting with all the symptoms. In contrast, naturopathic physicians frequently opt for a TSH level <2.5 with a goal of 1-2 for optimal health.

Second, a sole TSH lab test can be misleading, especially in cases of autoimmune thyroid disorders such as Hashimoto’s where circulating hormone levels can fluctuate wildly. In these cases, often the TSH falls within the normal range and can even be optimal but the actual circulating hormones in the blood are usually low or high in active inflammatory states.

For these reasons, it’s important to also check circulating free thyroid hormone levels, specifically Free T3 (FT3) and Free T4 (FT4). Screening with all 3 tests will provide the better picture of not only how the brain is signaling to the thyroid gland but also how the thyroid is responding and producing hormone for every cell of the body.

Assessing for Autoimmune Thyroid Disease

In the case of low thyroid function, called hypothyroidism, additional testing may be completed to assess for autoimmune thyroid disease. Specifically screening two antibodies, Thyroid Peroxidase antibodies (TPO) and Thyroglobulin antibodies (TG), can evaluate for Hashimoto’s disease.

Hashimoto’s thyroiditis is the most common cause of hypothyroidism and the most prevalent autoimmune disorder in the United States. Also known as chronic lymphocytic thyroiditis, Hashimoto’s causes the chronic inflammation of the thyroid gland due to antibodies that attack the thyroid hormone and gland, leading to gradual decline in function. Thyroid antibodies have indeed been found to be a marker for future thyroid disease even when all other thyroid markers are normal. Hashimoto’s can often go undiagnosed for years due to “normal” TSH levels as well as a lack of additional testing in conventional medicine. Sadly, for many of those with this condition, the thyroid gland is slowly destroyed over time until it can no longer produce enough thyroid hormone, and they are ultimately classified as hypothyroid.

The Value of Testing Beyond TSH

It is important to note that the thyroid gland is also vulnerable to imbalances of the endocrine system. Hormones such as estrogen, progesterone, cortisol, and testosterone have a major influence on thyroid enzymes, transporting proteins, and receptor site sensitivity. Testing for these is crucial. Many times, other endocrine imbalances are the culprit in thyroid imbalance, and restoring these imbalances has the greatest promise in supporting thyroid metabolic dysfunction.

In conventional medicine, additional testing is often overlooked because treatment options are limited solely to thyroid hormone replacement. In other words, conventional medicine typically addresses only thyroid hormone levels (the symptoms) and not any underlying conditions (the cause). As a naturopathic physician, and as well as having experienced undiagnosed hypothyroidism for years, I disagree with this notion. I find it important to screen for underlying conditions that can cause hormonal imbalances.

Please know that there is always something you can do about any potential thyroid or other underlying hormonal condition, and a request for additional testing is a good place to start. Be educated about your testing options, always ask for a copy of your lab work, and don’t be shy about letting your doctor know if symptoms have not improved with your current treatment. Naturopathic physicians have many tools to treat and rebalance the body. At NaturoMedica, we encourage you to not settle for anything less than optimal when it comes to your health.