9 thyroid tests you need to know if your thyroid is healthy

Why standard testing falls short

Today’s mainstream clinical practices surrounding the detection and treatment of thyroid conditions are lacking. This predicament has left many thyroid sufferers without answers. Inadequate lab testing along with a huge reference gap in lab ranges leaves many thyroid conditions undetected and untreated.

It is estimated that 20 million Americans have some form of thyroid disease; these numbers continue to increase each year. Nearly 60% of those with thyroid disorders are unaware of their condition (1).

Undiagnosed thyroid conditions put patients at risk for additional serious conditions, such as heart disease, infertility, osteoporosis, and weight gain/loss (1). Other common thyroid-associated issues include, but are not limited to, poor fat digestion, gallstones, fatigue, brain fog, constipation, diarrhea, infertility, and joint pain.

Pregnant women with hypothyroidism and subclinical hypothyroidism have a higher risk of miscarriages and have a greater chance of giving birth to children who have congenital defects and/or developmental conditions (1).

When mainstream testing standards finally do detect thyroid disease, an affected individual has likely had to suffer for a long period of time. Often, thyroid conditions are not detected until they have reached the full-blown disease stage. Early detection would undoubtedly improve clinical outcomes (2).

Today’s standard lab tests and ranges

It is common practice among mainstream medical professionals to measure the thyroid-stimulating hormone (TSH) with bloodwork to assess thyroid function. However, TSH is not an accurate marker for thyroid function when measured alone. Even with the addition of one or two thyroid hormone markers, it is still not enough information to confirm that there is or is not a thyroid condition present.

These standards need to change, but until then, there will be many who suffer for years, if not an entire lifetime, with an untreated and undetected thyroid condition.

Thankfully, there are alternative or holistic healthcare professionals who understand this issue and have pursued further education on the detection and diagnosis of thyroid conditions, but we need more education to support the millions struggling with thyroid-related illness today.

How thyroid hormone works in the body

Thyroid hormone output is controlled by the stimulation of TSH in a healthy functioning thyroid. (Note the word “healthy,” as a diseased thyroid will not be able to generate adequate amounts of thyroid hormone.) The thyroid hormone releases from the thyroid gland in response to TSH. These thyroid hormones are called Thyroxine (T4) and Triiodothyronine (T3).

Many processes within our body will not function as they should without adequate thyroid hormone. In fact, it is believed that every cell in our body has thyroid hormone receptors.

When thyroid hormone is present, it is transported into the cell where it binds to a nuclear receptor. This then initiates a process called transcription — responsible for the reading of genetic material that can then be translated into specific proteins used for physiological function throughout the body.

Since T3 activates transcription, the processes that T3 is specific to do not occur if T3 is not present. An example of this would be myosin, a cardiac protein responsible for increasing contractility of the heart. Adequate T3 is needed for the production of myosin. A lack of myosin results in reduced contractility of the heart muscle and, ultimately, the cardiac complications that may be seen with hypothyroidism.

Thyroid hormones help regulate:

• Basal Metabolic Rate (BMR)
• Heart rate
• Body weight
• Muscle strength and control
• Central and peripheral nervous systems
• Bone maintenance
• Fat digestion and lipid levels in the blood (increased cholesterol, LDL, and/or triglycerides can be indicative of low thyroid hormone)
• Menstrual cycles
• Mood
• Breathing rate/rhythm

The nine tests, one by one

Given the importance of thyroid function, it is essential to properly test it. For an accurate assessment, the following laboratory blood markers should be tested:

Test 1: TSH

The demand for thyroid hormone output is controlled through a feedback loop involving the hypothalamus and the pituitary. As blood levels of thyroid hormone decrease, the hypothalamus releases thyroid releasing hormone (TRH), which signals the pituitary to release thyroid stimulating hormone (TSH). The TSH then acts upon the thyroid, signaling the need for an increase in thyroid hormone output (T4 and T3).

In a perfect scenario, an increase of TSH results in an increase in thyroid hormone output, and a decrease in TSH results in a decrease in output. Once the body reaches sufficient output, TSH should respond by lowering (when there is enough hormone) or rising (when there is not enough). This inverse relationship is why a high TSH can be seen in hypothyroidism and a low TSH in hyperthyroidism.

Unfortunately, this perfect scenario is not how it always works out in real life. TSH is not always so intuitive.

Reasons you need more than just TSH tested:

• You can have a TSH well within lab range and still have low thyroid hormone output. TSH is not a direct measurement for thyroid hormone and may not reflect actual thyroid function.
• A malfunctioning Hypothalamus-Pituitary-Adrenal (HPA) axis can result in a poor TSH feedback loop.
• Literally any other thyroid marker indicative of dysfunction can be out of lab range, and this may or may not be reflected in TSH. In fact, this is very common.
• TSH can be within lab range in early stages of thyroid disease. This is where measuring thyroid hormones and antibodies, perhaps even a thyroid ultrasound, can be helpful.
• In autoimmune conditions, the thyroid is commonly destroyed slowly over time. This cannot be reflected by TSH until a significant amount of thyroid tissue has been destroyed.
• Lab ranges are very forgiving — they are based on the averages of the local population. This does not mean it’s an optimal range, just comparative figures.
• With thyroid hormone replacement, TSH is not an accurate measurement for adequate dosing. Thyroid hormones need to be measured as well.

TSH upper limit. There is much debate among researchers and clinicians as to what the standard upper limit for TSH should be, with several parties believing it should be lowered. When risk factors for thyroid disease are excluded, the upper reference limit is considerably lower in healthy individuals than the standard lab range.

In 2002, researchers published results of a large sampling of the U.S. population and determined that the mean TSH value of healthy individuals was 1.5 mIU/L (3). Another study looked at 870 individuals deemed healthy based on TSH alone; only 453 actually had healthy thyroids when evaluated according to the National Academy of Clinical Biochemistry (NACB) guidelines, which included measuring thyroid hormones and utilizing ultrasound imaging (4). NACB has recommended an upper limit of 2.5 mIU/L for TSH.

At Genesis Functional Wellness, we consider a healthy TSH to be 0.5–1.5 uIU/mL despite the local lab range listed as 0.45–4.5 uIU/mL. Keep in mind, we adhere more to a functional lab range. There is usually wiggle room for numbers as long as the whole picture makes sense and the person feels well. In our experience, we have seen suboptimal thyroid hormone markers with a TSH of 2.0 uIU/mL.

Tests 2 and 3: T4 and T3

When TSH is stimulated, both Thyroxine (T4) and Triiodothyronine (T3) are released from the thyroid gland. Both are bound by carrier proteins. T4 is the storage or inactive form of thyroid hormone and makes up about 93% of the thyroid hormone output. T3 is the active form and makes up about 7% of this output.

Thyroid hormone conversion. As thyroid hormone circulates peripherally, T4 is converted to T3 by an enzyme catalyst called 5’ deiodinase. T4 is converted at different points as it circulates through the bloodstream.

• The largest amount (60%) of conversion occurs in the liver. A healthy functioning liver is a large piece of ensuring conversion.
• The GI tract converts T4 into T3 sulfate (T3S) and triiodothyroacetic acid (T3AC) until it is acted upon by intestinal sulfatase, becoming T3. It is responsible for approximately 20% of conversion — yet another reason to have a healthy microbiome.
• Another portion (approximately 20%) is converted into reverse T3 (RT3), an inactive form of T3. In cases of illness or extreme stress, RT3 conversion can increase. Not only does it not provide the active effects of T3, it also competes at the nuclear receptor sites with T3 — lowering T3’s ability to elicit its effects.

Test 4: Reverse T3

This test is not commonly ordered, because most doctors do not think it is necessary, as they are not trained to interpret it. However, this test is highly valuable.

Higher than normal RT3 (inactive hormone) means less T3 (active hormone). This is a problem, because high RT3 levels will slow down metabolism and reduce thyroid function — which can result in the patient feeling hypothyroid. When RT3 is greater than 15 ng/dL, we start investigating why this number is elevated. Once the source is addressed, the RT3 will start to fall back into a normal range.

Reverse T3 becomes elevated with:

• Stress (high cortisol)
• Trauma
• Calorie restriction diets (5)
• Inflammation
• Infections
• Toxicity
• Zinc deficiency
• Selenium deficiency
• Certain medications

Tests 5 and 6: Free T4 and Free T3

Remember that both T4 and T3 are bound by carrier proteins. Because of this, they are unable to be used by the cells until they become what we call “free.” Researchers do not know exactly when this happens.

The free thyroid hormone is able to bind to the nuclear receptor to be utilized by the cells for metabolic purposes. These free thyroid hormones are called free T3 (FT3) and free T4 (FT4).

Test 7: T3 Uptake & TBG

T3 Uptake or Thyroxine-binding globulin (TBG) should be ordered to help assess the amount of carrier protein in the blood. These two tests measure differently but give similar information. (Carrier proteins are those that attach to the thyroid hormone released from the thyroid; when they lose the protein, they are called free T4 and free T3.)

T3 Uptake is a way for practitioners to measure the amount of sites available for thyroid hormone to bind to carrier proteins for transportation — an indirect measurement of the amount of thyroxine binding proteins. It is typically measured as a percentage; the lab range is typically 24–39%, and the functional range is about 28–38%.

• T3 Uptake will be low where there is excess estrogen (estrogen dominance), or even if there is low thyroid hormone but normal or adequate levels of estrogen.
• T3 Uptake will be high where testosterone levels are elevated — found in conditions like PCOS, insulin resistance, hirsutism, and the intake of testosterone hormone.

TBG makes up a majority of the proteins that transport thyroid hormone throughout the body. High levels of TBG will result in lower free hormone levels, decreasing the amount of hormone able to enter the cells (FT4 and FT3) — so it can result in hypothyroid symptoms even with adequate thyroid hormone output. T3 Uptake and TBG have an inverse relationship: high TBG with low T3 uptake, and low TBG with high T3 uptake.

Tests 8 and 9: Thyroid antibodies (TPO, Tg)

Elevated thyroid antibodies can be found in thyroid diseases like Hashimoto’s and Graves’. Lab-high antibodies are needed for an autoimmune diagnosis, although an autoimmune disease of the thyroid gland can be present before thyroid antibodies are lab high or even detected.

This mechanism begins when the body’s own immune system creates antibodies to thyroid tissue. There are many stressors thought to induce this response.

Some mechanisms that can lead to thyroid antibody production:

• Transfer of antibodies from the mother in utero (6)
• Dysbiosis (leaky gut) (7)
• Infections (EBV (9), Bartonella, Lyme, Yersinia, H. pylori (10), etc.) (8)
• Environmental toxins (mold, heavy metals, chemicals) (11)
• Stress (emotional and/or physical) (12)

Hashimoto’s. Iodine deficiency is the most common cause of hypothyroidism worldwide (13). However, autoimmune thyroid disease is the most common cause of hypothyroidism in the United States (14). This form of autoimmunity, known as Hashimoto’s, is 5–10 times more common in women than men (15), and the incidence increases with age. It is assessed with Thyroid Peroxidase (TPO) antibodies and Thyroglobulin (Tg) antibodies.

Additional tests & imaging

Graves’ disease antibodies. Graves’ disease is marked by the overproduction of thyroid hormone due to an autoimmune process on the thyroid gland. Its antibody tests are: TSH antibodies (16), Thyroid Receptor (TR) antibodies, Thyroid Peroxidase (TPO) antibodies, and Thyroglobulin (Tg) antibodies.

Thyroid ultrasound. Thyroid ultrasounds are a very effective diagnostic tool, providing a high-resolution image of the gland. Ultrasounds show evidence of thyroid dysfunction before any lab work does, and abnormal nodule findings can indicate a need for further testing.

Thyroid ultrasounds are used for:

• Early detection of thyroid disease
• Follow-up for abnormal thyroid blood work
• Abnormal findings in physical exam of the neck (17)

Thyroid ultrasounds will show:

• Swelling (indicative of thyroiditis or an autoimmune condition)
• Blood flow throughout the gland
• Abnormalities (cysts, nodules, tumors)
• Nodule features (some strongly correlate with a benign nodule while others correlate with cancer) (17)

Thyroid disease lies beneath many health issues, but using these testing methods will reveal what’s happening so individuals do not have to suffer as long.