One of the first things I do with new patients is order comprehensive lab tests, if they don’t have recent ones already. And one of the things I make sure to test — comprehensively — is the thyroid.
why thyroid hormones matter
The thyroid is a butterfly-shaped gland on the front of your neck, just under the Adam’s apple. It’s responsible for how quickly or slowly your body uses energy, and plays a large role in processes including digestion, bone health, heart function, mood and fertility.
Too much thyroid hormone (hyperthyroidism) can make you feel speedy, hot, sleepless, sense your heart racing, and lose too much weight.
Too little thyroid hormone (hypotheyroidism) can cause lethargy, coldness, dryness, constipation, hair loss and depression.
If your thyroid just isn’t optimal, you may feel a little bit off. But sometimes thyroid testing reveals deeper problems, including autoimmune diseases. So I check thyroid levels to make sure you’re at your best — and to catch or follow any serious health issues.
how thyroid hormones are tested
We can check your thyroid levels with a simple blood test, along with other labs that screen for anemia, diabetes, cholesterol, immune and organ function.
There are three main things aspects of thyroid health we test for:
- What signals your brain is sending to your thyroid gland. Does it want you to make more? Less? Or are you just right?
- How much thyroid hormone is circulating in your body, and there are different kinds.
- Whether your immune system is reacting to your thyroid.
I don’t always test that third parameter, unless my patient has signs and symptoms suggesting deeper thyroid pathology. In those cases, we are checking whether your body is treating your thyroid gland or its products as an invader — a condition known as autimmunity. If you do have an autoimmune thyroid disorder such as Grave’s Disease or Hashimoto’s thyroiditis, these can lead to higher or lower levels of functional hormone in your body.
signals from your brain
If your doctor checks your thyroid health, they most commonly use a single test called thyroid stimulating hormone, or TSH. (It’s the yellow arrow in the image below.)
Understanding this test can be a little confusing, since it generally represents the opposite of how much active thyroid hormone you have. Remember, this is the brain talking to the thyroid gland, telling it whether to make more or less. If the thyroid isn’t producing enough hormone, the brain gives it louder signals. If the thyroid is overproducing, the brain starts to whisper.
Key hormones and feedback loops regulating systemic thyroid hormone production.
So a high TSH suggests low circulating hormone, (hey, thyroid! make more hormone!) and a low TSH level means high circulating hormone (calm down, thyroid, we don’t need that much.)
hormones in your circulation
While TSH gives you some important information about thyroid function, it doesn’t really give you a full picture. That’s why I like to check actual levels of two thyroid hormones in your body — because sometimes the brain misreads things. (More on tht in a minute.)
Why two? Because they’re each different — and both important.
When I explain circulating thyroid hormones to my patients, I tell them to think of glow sticks. You know the ones, where they’re dark in the box but light up when you crack them. Or handwarmers that don’t heat up until you shake them.
Thyroxine, or T4, is the unlit glow stick. It circulates in your body without lighting anything up. Thyroxine gets its name (T4) from its chemical architecture, which includes four iodine molecules that sit like towers sticking out of rings. When a local tissue requires active hormone, the T4 gets activated and goes to work.
The activated version of thyroid is triiodothyronine, or T3. It’s just like the T4, but with one of the iodine removed to light it up. Most of what’s in your body is locally converted T4, but some of this hormone circulates, too.
T3 through the looking glass
When people’s thyroid labs don’t make sense — their T4 and T3 levels are fine, but their TSH or symptoms suggest they don’t have enough thyroid hormone — I look at another test: reverse T3.
Both physiology and chemistry often rely on shape recognition. And in the same way that a left glove won’t fit on a right hand, where that one iodine gets removed from the T4 matters. While T3 will fit into receptors to support metabolic function, mirror-image reverse T3 does not.
I apologize for making you look at chemistry, but the main thing to note here is the location of the red I(odine)s and how they’re different in functional vs non-functional reverse T3.
The architecture of three versions of thyroid hormone makes a signicant difference in the body. Thyroxine, or T4, has four iodine molecules, marked in red. Triiodothyronine or T3 has three iodine molecules marked in red. Reverse T3 also has three iodine molecules, but in a different configuration from functional T3, making the hormone ineffective in the body.
Unfortunately, parts of the brain that track circulating thyroid hormone levels can’t tell T3 and its mirror image apart. If the brain doesn’t see the difference, it doesn’t note the effective deficiency. Then it doesn’t tell the thyroid to do more. And then you feel worse and worse without knowing why.
(This is another reason why testing TSH alone doesn’t offer a full picture.)
what makes the thyroid wonky?
Thyroid levels can get wonky for many reasons, ranging from nutrient deficiencies and stress to immune irregularities to cancer.
Iodine is foundational to thyroid hormones, as we saw with the chemistry lesson (sorry!) above. Too little iodine leads to a condition where the thyroid gets large (goiter,) and becomes less effective at creating its hormones. Goiter used to be common around the world, and has been largely eliminated by the introduction of iodized salt. (I love natural salts of many kinds, but getting your iodine is important!)
Compounds in certain foods also may keep the thyroid from operating optimally. One main class of culprits here are the Brassica family of vegetables when eaten raw. These include health-promoting foods like kale and collards and broccoli. You absolutely can eat these foods safely; just follow some basic guidelines.
Cancer is beyond the scope of this post. But diagnosing thyroid cancer includes changes to the thyroid that you or your doctor can touch, lab testing, imaging, and biopsy to identify abnormal cells.
autoimmune thyroid is a growing problem
Most of the time, making dietary changes, addressing stress, or supplementing with herbs and vitamins is enough to return the thyroid to healthy function.
But increasingly we are seeing autoimmune thyroid disease, in which the immune system starts to attack parts of its own body.
We don’t know all the reasons why this happens. Some of it is genetic, but not all folks with the predisposition end up with autoimmune diseases. Hormonal changes can trigger autoimmunity, and we often see these conditions arise around major life stressors, pregnancy, and perimenopause and menopause. These can also show up after viral infections, or in conjunction with allergies or food intolerances.
I check for autoimmune thyroid when people are at these crossroads, have unexplained symptoms consistent with thyroid dysfunction, or have a family history of autoimmune thyroid conditions.
what’s the best way to test thyroid hormones?
For many years, mainstrream medicine has only tested TSH, sometimes with T4 and sometimes not. But new research supports what naturopathic doctors have been doing for years: keeping an eye on active T3 as well.
Here are the basic labs I run when screening patients for thyroid health:
- Thyroid stimulating hormone (TSH)
- Free T4
- Free T3
When I suspect deeper levels of dysfunction based on a patient’s symptoms or family history, we may also test the following:
- Reverse T3
- Thyroid peroxidase antibodies (Hashimoto’s thyroiditis)
- Thyroglobulin antibodies
- Thyroid stimulating immunoglobulin (Grave’s Disease)
- Thyroid stimulating hormone receptor antibodies (Grave’s Disease
Usually we’re not testing thyroid in isolation, but also looking at other parameters of health such as blood sugar, cholesterol, organ function, immunity, anemia and inflammation. The exception is when we’re specifically checking to see how treatment is working.
I hope you found this review helpful, and that it will help you get the most out of your doctor’s visits. If you’re in Alaska or Oregon and would like to talk about thyroid health with me, click the button below to make your appointment.
Salúd!
—Dr. Orna
Header photo by National Cancer Institute on Unsplash.
