I’ve heard the story hundreds of times in one form or another. There’s the fatigue, weight gain, depression, hair loss, constipation, dry skin, irregular periods, maybe fertility problems, a miscarriage – or both – or intense fatigue and difficulty producing enough breast milk after you’ve had your baby. You convince your doctor to test your thyroid because you’ve read that thyroid labs could be causing these symptoms. She does and tells you, upon reviewing the results, that your thyroid isn’t the problem. It’s probably just stress, the fact that perhaps you had a new baby and are naturally exhausted and overwhelmed, that miscarriages are common and you can try again, or that perhaps you are really just emotionally depressed and should take an antidepressant. Then time passes. Maybe you take the antidepressant, maybe you don’t. But the symptoms don’t really go away. You’ve gained more weight, you’re more tired, and this whole situation is so depressing that you start to wonder if you really do have a mental health problem.
In desperation, you go to a different doctor. She orders a more complete range of tests because now that you’ve done your research using “Dr. Google,” (or Dr. Aviva!) you know what to ask for. Perhaps you had to insist – but either way she ran the tests. And voila, after all of these months of suffering and worrying, guess what, you really do have a thyroid problem!
The Thy-Gap: Why Thyroid Tests Don’t Always Reveal the Whole Picture
Most of us, whether as doctors or patients, have been led to believe that medical guidelines and practices are pretty much set in stone, and are based on hard reliable facts. The former is definitely not true, in fact, in just the past 5 years or so, it's been found that many long-followed medical guidelines aren't correct – guidelines have changed at least on the following: when and how often women need pap smears, how often women need mammograms, the safety of and when to use statin drugs, the safety of and when to use aspirin to prevent heart attack, the safety and use of ibuprofen and other NSAIDS, whether men need the PSA test, how long women should be in labor before they are induced, the level of blood pressure at which high blood pressure should be diagnosed in otherwise healthy adults over 50, the level at which diabetes should be diagnosed …. and I could go on.
It has been found that sometimes, doing tests or interpreting them inappropriately can even lead to harm. For example, hundreds of thousands of young women had pap smears that led to LEEP procedures and cone biopsies that caused scar tissue to the cervix that ultimately led to difficulty dilating in labor when they eventually had children. We now know that women under 21 years old should never have a pap smear because the results aren't useful in that age for a variety of reasons I won't belabor here.
Perhaps an even more closely related example that parallels thyroid testing is lead testing. Until just a couple of years ago, kids had to have a lead level > 10 to be diagnosed with lead toxicity. Integrative and functional doctors have been saying that number is too high for years – decades even. It was only recently determined that in fact, at lead levels of over 5 kids can experience damage due to toxicity, thus the standard range of normal was lowered.
On top of this, medical guidelines, while based on hard data, are only as good as the data they are based on, and on what's known at the time the guidelines are made. So for example, the TSH lab values for normal are based on TSH averages for most generally healthy Americans. But many Americans are under- diagnosed for thyroid disease. When we take an expanded view of thyroid health, and only include the TSH average of people with absolutely no hypothyroid symptoms, the number changes. I'll tell you more about this in a minute.
The truth is that the correct set of thyroid tests, along with proper interpretation of the results, usually does tell the whole truth about your thyroid health. The problem is that:
- Most doctors don't order a complete set of thyroid labs initially, and only do so if the initial result is abnormal, and
- Most doctors are taught a limited set of parameters for interpreting lab tests that don’t always catch everyone with a thyroid problem, particularly Hashimoto’s thyroiditis, or autoimmune hypothyroidism.
As with the lead testing parameters, until recently when the range for normal was made narrower, thus catching more kids with elevated blood levels lead at risk of toxicity, the TSH range for normal starts too high – in fact, until not long ago, it was even higher than it is now – leaving many women with hypothyroidism undiagnosed, sick, and untreated.
As many as 10% of all Americans have a thyroid problem, mostly women, and many have a slow functioning thyroid and just haven’t been properly diagnosed. In a world where medical over-testing is rampant, I have to say, I find myself confounded by the fact that so many physicians are resistant to ordering anything but a TSH – or thyroid simulating test – as the first form of evaluation, when from a scientific and medical standpoint, that test can be normal and there can still be a low functioning thyroid. It’s outdated medical dogma to order solely this test, and I almost always order a full panel when I am presented with a patient with common symptoms of hypothyroidism.
As for the limited interpretation of thyroid labs, this is because there are differences of opinion between various professional medical groups as to how high the TSH should be before we diagnose someone with hypothyroidism. This leads to what I talked about on Dr. Oz – the “thy-gap” – in which you might have thyroid symptoms, and in fact hypothyroidism, but according to your doctor, your labs are normal.
In fact, not many years ago, that number was a lot higher than it is now; so many more women were told they had normal thyroid function when they did not. Many of us contend that this number is still too high, and in fact, when you test the general public who have no symptoms of hypothyroidism, the average TSH is much lower than the number used to decide whether you have a thyroid problem. If that number were brought down closer to the healthy thyroid general public, more women who have thyroid symptoms would get a diagnosis. Now I’m not for over-testing or over-diagnosis of any sort, but I’m also not for women suffering with symptoms that they are told are probably just in their heads – when they are not!
Read on to see if you should have thyroid testing, what to get tested for, and what results indicate that you might have a thyroid problem.
When to Get Thyroid Testing
Here are some of the most common symptoms of a slow functioning thyroid that suggest thyroid testing might be a good idea:
- Cold intolerance
- Goiter (swelling in the front of the neck)
- Impaired memory
- Menstrual disturbance
- Miscarriage, especially with any of these other symptoms
- Muscle cramps or weakness
- Nerve pain, carpal tunnel syndrome
- Postpartum depression
- Slow heart rate
- Slowed mental processing
- Slowed physical movements
- Swelling or puffiness around the eyes
- Weight gain
Also, if any of these lab results is part of your medical story, thyroid testing should be done:
- Anemia with large red blood cells (macrocytic anemia)
- High cholesterol
- High serum muscle enzyme concentrations
- History of autoimmune disease
- Low sodium
The Thyroid Labs I Recommend
There are 6 key tests that can unlock the mystery of your thyroid function and are what your doctor should be looking at. Thyroid testing should be simple to obtain from your primary doctor or local lab. However, the nuances may take some skill to interpret, depending on the results, and your doctor might be resistant to ordering more than the TSH test. That’s where an open-minded endocrinologist or a skilled Functional Medicine doctor can be of help!
In my practice, if my patient’s symptoms are highly suggestive of hypothyroidism, I will run the entire thyroid panel described below right from the start. If there are other diagnoses that are equally likely to explain the symptoms, I will run just the TSH, FT3, and FT4 while testing for other causes, for example, anemia, other autoimmune conditions; if the thyroid labs come back borderline or positive for thyroid or thyroid hormone problems, I will then add in the remainder of the tests. I will also sometimes recheck test results for TSH, FT3, and FT4, if normal in a newly symptomatic patient, in 6-12 weeks, because I’ve occasionally seen initial testing be normal then a short time later, voila – the tests come back confirming the problem.
Thyroid Stimulating Hormone (TSH)
Thyroid Stimulating Hormone (TSH) is produced in a part of your brain called the pituitary gland. The job of TSH is to tell the thyroid gland that it’s time to get busy producing more thyroid hormone. When the healthy thyroid gets this chemical message, it produces two hormones: triiodothyronine (T3) and thyroxine (T4), The normal range for TSH is somewhat controversial. Most labs consider the upper range to be between 4 and 5 mU/L. However, many experts – even in conventional endocrinology – believe that the upper end of normal is actually more like 2.5-3 mU/L. This is based on the fact that when Americans without any hypothyroid symptoms have this test done, that is the most usual upper range.
Many integrative and functional medicine doctors find that their patients feel their best at an upper limit of 1.5-2 mU/L.
My patient was one of these people. At a TSH of 4 she was really at the upper limit of normal, over the preferred upper limit according to some docs, and well over the 1-2 mU/L upper range! This controversy and discrepancy of opinion over the normal upper range for TSH is one of the most common reasons that women get under-diagnosed for hypothyroidism and suffer with unnecessary symptoms that can seriously interfere with health and quality of life.
In most cases hypothyroidism occurs because the thyroid gland is sluggish – that is, it is having trouble producing T3 and T4. This can be due to a variety of reasons ranging from nutritional deficiencies to autoimmunity. So TSH gets pumped out in a higher amount to try harder to stimulate the thyroid gland into action. Think of it like this: You are TSH. Your best friend’s house is the thyroid gland. When you go to visit your friend you knock on her front door. If she doesn’t answer, what do you do? You knock louder to get a response. In just the same way, the TSH amps up to knock louder, hoping to get an answer. That’s why an under-functioning thyroid shows up as high TSH on lab tests. However, TSH can be normal in the presence of hypothyroidism in some cases, and you can still be having the symptoms of low thyroid when TSH is normal because of poor conversion of T4 to T3 (see below) or because of thyroid hormone resistance at the level of your cells.
When stress is suppressing the pituitary gland enough to interfere with producing TSH, you might see low or normal TSH levels in the presence of low thyroid hormone production (T3 or T4), and hypothyroid symptoms.
Thyroid Hormones (T3 and T4)
Triiodothyronine (T3) and thyroxine (T4) are the hormones produced by your thyroid gland. T4 is produced in a much larger amount and is then converted to T3, the active form of the hormone, as needed to up-regulate metabolic functions. T3 and T4 are sent out into your bloodstream where they are responsible for the thyroid’s actual work of controlling your metabolism. Free T3 (FT3) and Free T4 (FT4) are called this because they are not bound to proteins in your blood, making them free to perform their work in your cells – keeping your metabolism appropriately revved up for your optimal health.
Measuring FT3 and FT4 is important because they are the indicators of thyroxine and triiodothyronine activities in the body. A high TSH and low FT4 and FT3 indicate hypothyroidism. A normal TSH, normal FT4, and low FT3 can indicate T4 to T3 conversion problems, and a normal or high TSH, normal FT4 and high FT3 can indicate cellular resistance to FT3 which can still lead to hypothyroid symptoms because the active hormone can’t get to the cell to do its job.
Thyroid antibody testing is ordered to diagnose autoimmune thyroid disease and distinguish it from other forms of thyroid dysfunction.
The two thyroid antibody tests that I order are Thyroid peroxidase antibody (TPOAb) and Thyroglobulin antibody (TgAb). Some people do have an autoimmune thyroid condition but don’t initially test positive. If positive, antibody testing can be repeated every six months to trend improvement while you are working with an integrative physician to address possible underlying causes.
Reverse T3 (rT3)
Reverse T3 is the third most abundant form of thyroid hormone. When your body wants to conserve – rather than “burn” – energy, it will divert the active T3 into an inactive “reserve” form. This might happen when you are sick, under stress, or undernourished. If TSH and FT4 look ok, but FT3 is low this can be because it is being diverted into rT3 – which will be elevated. It is worth checking rT3 if there are obvious symptoms suggesting hypothyroidism, but the typical tests aren’t demonstrating low TSH or low FT4. There is some controversy among conventional doctors about the utility of this test – I personally find it very useful.
Interpreting Thyroid Labs Properly
As I stated earlier, most doctors are taught a limited interpretation of thyroid labs, in which hypothyroidism is diagnosed only when the TSH is above about 4.5 to 5.0 mU/L. However, a paper published by the National Academy of Clinical Biochemistry argues that the upper limit of normal should be reduced to 2.5 mU/L because 95% of rigorously screened volunteers with no symptoms and healthy thyroid function have serum values between 0.4 and 2.5 mU/L and a large study from Germany found a normal reference range of 0.3 to 3.63 mU/L. Controversy also exists as to whether those with a TSH of between 5 and 10 mU/L need to be treated, even if they have symptoms.
Over 2.5 in the first trimester, and 3.0 in the second and third trimesters are considered the upper limit for TSH in pregnancy, and indicate the need for treatment.
In my practice, if the level is over 2.0 mU/L and there are symptoms, I treat for hypothyroidism, even if someone is not pregnant. If there are no symptoms at all, and the level is under 3.5, I usually don’t treat, but I then trend thyroid levels for the next 12 months, testing again in 3 months, then again 6-9 months later, and I test for thyroid antibodies, because often thyroid antibodies are a harbinger of thyroid problems to come.
If TSH is normal, but FT3 is low, then I might supplement with FT3 only, and I explore factors that might lead to poor conversion of FT4 to FT3. I also check reverse T3 (rT3) because stress, infection, inflammation, elevated cortisol, and poor nutrition, among a number of factors, can cause the body to divert FT4 to rT3 in an effort to “lower the body’s thermostat” and conserve energy by slowing down the thyroid. This is a biological protection mechanism, similar to setting the thermostat at lower temperature during an energy crisis.
TSH, FT3, and FT4 can also be normal when there is thyroid hormone resistance – the thyroid is working just fine, but thyroid receptors on cells aren’t letting thyroid hormone in, so it can’t do its jobs. This can be a result of high cortisol due to stress, infection, or inflammation, and may also be associated with high homocysteine, which can occur when there is an MTHFR genetic change, which can be tested for by your doctor or a local lab. If present, methylfolate, 800-1000 mcg/day for adults, is usually recommended to accommodate for the genetic change.
The most important takeaway here is that in order to get to the bottom of your symptoms, and get appropriate treatment, you have to start with a proper diagnosis. I hope you are able to use this article to discuss your symptoms, thyroid labs, and thyroid results with your care provider to get the answers you need, and the treatment that will help you to feel better!