by Dr. Will Cole
With around 20 million cases in America alone and 200 million people worldwide, hypothyroidism, or low thyroid function, is one of the most common underlying chronic hormonal problems in the world. Many health professions consider it a silent epidemic because probably half of those struggling with this insidious health problem remain undiagnosed and don’t know why they are suffering with frustrating and debilitating symptoms like unexplained weight gain, fatigue, hair loss, brain fog, depression, anxiety, or digestive problems.
If your thyroid isn’t working well, nothing in your body works well, but diagnosing a thyroid issue isn’t easy because lab test results can be confusing and misleading. If your doctor only tests for your level of thyroid-stimulating hormone, or TSH, then you will only get treated (with a synthetic thyroid hormone like Synthroid or levothyroxine) if your labs are out of range. If your labs come back “normal,” you will probably be sent home with a shrug or an assurance that you are fine. In my view, this is a serious problem.
How Labs Determine “Normal” Ranges
If you have the symptoms of low thyroid hormone but your TSH is “normal,” something is not being addressed. Part of the problem starts with the reference range for what is considered normal. How do we get the “normal” lab range? The reference range is based on a statistical average of the population getting tests out of the lab. This is why (other than for vitamin D and cholesterol levels) lab reference ranges will vary depending on the lab.
The people who get tested in labs – in other words, the population of that lab – are obviously statistically not the healthiest segment of the population. Otherwise, they wouldn’t be getting lab tests. That means if the lab results are “normal” despite your symptoms, what your doctor is essentially saying is you’re just like a lot of other sick people!
In functional medicine, we look at a much narrower range of normal, taking this into account. We want your labs to look like a bunch of healthy people whose bodies function optimally and who feel great.
Thyroid Labs: The Functional Medicine Version
A functional medicine look at your thyroid is more in depth than just a TSH and maybe a T4. We do a broader range of tests and look at a narrower range of optimal results. Here are some of the labs I run on my patients, what they actually mean, and what kind of results are ideal:
Thyroid-stimulating hormone is released from your pituitary gland to communicate with your thyroid. If your TSH is high, it’s sort of like your brain shouting at your thyroid to work harder. Research has linked a lab “normal” TSH of 2.5-3.5 mlU/mL with a 69% risk of dying from a heart attack or stroke. Now you can see why the optimal (functional) range is so important for your health. Forget the larger reference ranges and aim for what’s optimal:
Lab range: .45-5.5 mlU/L
Optimal range: 1.8-2.5 mlU/L
T4 is mostly metabolically inactive in the body and has to be converted to T3 to be usable. This lab gives you a total of unbound and bound forms of T4. Hormones have to be unbound from the protein carrier to be used by your body. Because of this, this lab doesn’t give us the activity of T4 when measured alone. T4 is measured in conjunction with a T3 uptake.
Lab range: 4.5-12 mcg/DL
Optimal range: 6.0-12.0 mcg/DL
This lab doesn’t look directly at T3, but is very useful at indirectly looking at other hormones such as estrogen or testosterone and their relation with the binding of thyroid hormones.
Reference range: 22-35%
Optimal range: 28-38%
This lab shows us the total amount of the metabolically active thyroid hormone. It allows a doctor to check your body’s ability to convert T4 to T3 and to rule out an overactive thyroid.
Lab range: 80-200 ng/DL
Optimal range: 100-180 ng/DL
This will tell you the levels of free or active form of T4. This will be low in cases of hypothyroidism but can be normal in subclinical, early stages of thyroid dysfunction.
Lab range: 0.8-1.8 ng/DL
Optimal range: 1.0-1.5 ng/DL
This is the more active, usable form of your thyroid hormone. Low T3 syndromes are a common dysfunction that I see in practice, and a low level of this hormone is strongly linked to a higher risk of heart attack. The problem, if you’re taking a synthetic T4 medication, is that your body isn’t converting the hormone properly into T3, though there are many reasons your thyroid medication may not be working.
Lab range: 2.3-4.2 pg/mL
Optimal range: 3.0-4.0 pg/mL
Chronic stress and high cortisol can raise levels of reverse T3, which is an unusable form of the thyroid hormone.
Reference range: 8-25 ng/DL
Optimal range: 9.2-24.1 ng/DL
High levels of thyroid antibodies show an autoimmune attack against the thyroid. The overwhelming majority of low thyroid cases are on the autoimmune spectrum, the most common being Hashimoto’s disease.
Thyroid Peroxidase (TPO) Ab optimal range: 0-15 IU/mL
Thyroglobulin Ab optimal range: 0-0.9 IU/mL
In addition to these thyroid-focused labs, functional medicine practitioners are likely to recommend additional labs to address your microbiome, immune system, and other hormones. These should also be considered for the most complete picture of what is going on with your health.
Getting the big picture from labwork is a solid first step towards finding out exactly what is going on with your thyroid. What conventional doctors may not tell you is that there are many thyroid dysfunctions that typically don’t show up on labs, and that throwing synthetic thyroid medication at the problem will, in many cases, not do enough to relieve symptoms. You can do more to help.
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