The Best Tests for Thyroid Function (Hint: TSH, T4 Aren’t Enough)

If random symptoms like weight issues, hair loss, and brain fatigue have you scratching your head, it may be time to check your thyroid function. Chronic thyroid imbalance can wreak havoc on your health. Sadly, many people struggle with confusing thyroid symptoms for YEARS before getting a diagnosis, which can damage the body. Conventional medicine has a one-size-fits-all approach when it comes to checking your thyroid health. Often, their testing tends to be limited — just like their treatment options.  Functional medicine takes a more holistic view of thyroid health for both testing and treatment. There’s an arsenal available of tests for thyroid function — you just need to know what to ask for. In this post, I’ll give you the inside scoop on the best tests for thyroid function available so that you can get answers asap…and get your body back in balance.

What is the Thyroid, and How Does it Work?

Ok, first things first — time for a biology review. Your thyroid is a butterfly-shaped gland that lives in your neck. It plays a crucial role in regulating your metabolism, blood pressure, heart rate, energy creation, bone density, gastrointestinal function, and even your mood! Your thyroid gland releases two main hormones: T4 (thyroxine) and T3 (triiodothyronine). If your thyroid is sluggish, you may not produce enough of these hormones, leading to a condition called hypothyroidism. On the flip side, if your thyroid is overactive, you’ll have too many of these thyroid hormones floating around — a condition called hyperthyroidism. But there’s another important player in the thyroid game: your pituitary gland. Your pituitary gland releases TSH (thyroid-stimulating hormone), which acts as the conductor of your thyroid orchestra. TSH triggers the release of T3 and T4, helping to keep your thyroid hormones in balance.

How Do I Know if I Need to Check My Thyroid?

Thyroid symptoms are all over the map — which is exactly why you can’t diagnose thyroid problems from symptoms alone. Proper testing is critical. Check out the medley of symptoms below, and you’ll see what I mean:

1. Common Symptoms of Hypothyroidism

  • Weight gain or weight loss
  • Fatigue
  • Dry hair
  • Hair loss
  • Dry skin
  • Feeling cold
  • Heavy or irregular periods
  • Trouble concentrating
  • Memory issues
  • Depression
  • Weakness or aching in muscles and joints
  • Slowed heart rate
  • Decreased sweating
  • Puffy face
  • Hoarse voice
  • Constipation

2. Common Symptoms of Hyperthyroidism

  • Weight loss
  • Increased appetite
  • Nervousness
  • Restlessness
  • Irregular heartbeat
  • Trouble concentrating
  • Coarse, brittle hair
  • Difficulty sleeping
  • Nausea & vomiting

What Factors Affect Thyroid Function?

Two massive risk factors for thyroid imbalance are gender and age. In fact, women are five to eight times more likely to develop a thyroid condition than men! People over age 60 are also at increased risk. However, there are a ton of other factors that can throw your thyroid off-kilter, including:

  • Genetics
  • Stress
  • Smoking
  • Poor diet lacking nutrients vital to thyroid health (such as selenium, iodine, and zinc)
  • Infections
  • Fluoride
  • Toxin overload
  • Certain medications
  • Autoimmune conditions (especially Celiac disease)
  • Inflammation
  • Liver or kidney dysfunction

Why Conventional Tests for Thyroid Function Often Misses the Mark

Tests for Thyroid Function

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The American Thyroid Association estimates that up to 20 million Americans are suffering from thyroid disease. What’s even scarier is that up to 60% of people with a thyroid condition are undiagnosed. Part of the undiagnosed dilemma is due to the random nature of thyroid symptoms that often mirror other health conditions. Also, many people with thyroid illness deal with multiple health challenges, which makes diagnosis tricky. However, a huge reason thyroid illness falls through the cracks is due to inadequate testing. Often if a conventional medicine doctor suspects thyroid disease, they’ll only test for TSH and T4. These tests supply only two small pieces to a much larger puzzle.

This lack of testing causes many people suffering from thyroid conditions to suffer needlessly and remain undiagnosed for years!  Your body works on “feedback loops” that communicate your environment to your brain. Feedback loops get triggered by environmental factors such as stress, liver issues, poor diet, trauma, gut problems, and much more. These feedback signals cause issues with thyroid conversion and create thyroid problems without having out-of-range thyroid numbers. That’s why it’s so important to be armed with the right information. Knowing what tests to ask for is the first step towards solving your health puzzle — so you can get on the road to recovery.

The Best Tests for Thyroid Function to Ask For

Tests for Thyroid Function

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Checking your thyroid function is done via blood testing. The following tests will help clarify whether you have a thyroid issue, how severe it is, and whether an autoimmune condition may be to blame. They are the best tests for thyroid function that can give you a complete picture of how your hormone is working. Did you know that the majority of hypothyroid cases stem from autoimmunity?

1. TSH (Thyroid-stimulating hormone)

TSH is the most common thyroid test conventional doctors order. Why? Well, TSH changes often show up before other thyroid markers are off-balance. As I said earlier, your pituitary gland produces TSH to stimulate your thyroid to produce more T4. Your pituitary and thyroid glands run on a feedback loop. If your pituitary senses low T4, it sends more TSH to the bloodstream to trigger T4. Alternatively, if a high T4 is detected, your pituitary puts the brakes on TSH. A high TSH level suggests your body is not producing enough thyroid hormones; a condition called hypothyroidism. A low TSH implies your thyroid is producing too many thyroid hormones, known as hyperthyroidism.

TSH Range: What’s the New “Normal”?

The TSH normal range has been hotly debated over the years. Previously, a “normal” TSH level was anything between 0.5 and 5.0 mIU/L. However, in 2002, the American Association of Endocrinologists realized this range was too broad, allowing patients with mild thyroid disorders to fall through the cracks. They revamped the target TSH level range to 0.3 to 3.0 mIU/L. When you get your test results, keep this in mind, as some doctors may still use the outdated range.

2. Total T4 (Thyroxine)

T4 is the most abundant thyroid hormone. In fact, research proves that of all the hormones your thyroid produces, 90% of it is T4! T4 is an inactive hormone that eventually gets converted into its active form, T3. Most T4 is bound to proteins and unavailable to your cells. Only unbound “free” T4 can enter and adjust your body’s tissues. A total T4 test measures the bound and “free” T4 floating around your system. Low levels of total T4 may indicate hypothyroidism, while high total T4 may indicate hyperthyroidism.

3. Free T4 (Free thyroxine)

Free T4 measures the amount of unbound T4 available to your cells. Believe it or not, only about 1% of all your T4 is unbound! For that reason, free T4 offers a much more accurate picture of your T4 levels.  T4 that is bound in the blood is unavailable to the cells. A low free T4 and high TSH suggests primary hypothyroidism, while a low free T4 and low TSH may indicate hypothyroidism due to a problem with the pituitary gland.

4. Total T3 (Triiodothyronine)

T3 is the other major hormone your thyroid makes, just in smaller amounts than T4. However, like with T4, the majority of your T3 is bound by transporter proteins. Only the unbound, “free” T3 can enter and affect your tissues. If you have symptoms of an overactive thyroid, checking your total T3 may be a wise move, as high total T3 is often found in patients with hyperthyroidism. However, be wary if you suspect hypothyroidism, as total T3 is usually the last test to show those abnormalities.

5. Free T3 (Free triiodothyronine)

T3 is an active hormone, meaning it can bind to hormone receptor sites. Free T3 measures the levels of “free,” unbound T3 available to your cells. High free T3 levels indicate hyperthyroidism, although it’s much more common for free T3 to be low.

6. Reverse T3 (Reverse triiodothyronine)

When reverse T3 is high, it means the body is converting most of its T4 into reverse T3 (instead of regular ol’ T3). At times, high reverse T3 serves as a red flag of a more severe illness such as non-thyroidal illness syndrome.

Thyroid Antibodies (The most overlooked of all the tests!!)

Your immune system’s job is to protect you from foreign invaders, such as bacteria, viruses, or parasites. It does this by destroying harmful pathogens with antibodies, substances made by your immune system’s lymphocytes. However, if your immune system gets disorganized, it can mistake healthy tissue for a foreign invader — and go into attack mode. This is known as autoimmunity and is the leading cause of hypothyroidism. The two autoimmune conditions that target the thyroid gland are Hashimoto’s thyroiditis and Grave’s disease. Hashimoto’s thyroiditis manifests with symptoms of hypothyroidism, while Grave’s disease presents with symptoms of hyperthyroidism. The following thyroid antibody tests give helpful clues about whether low thyroid function is due to Hashimoto’s thyroiditis:

  • Thyroid peroxidase antibody (TPOab) – Thyroid peroxidase (TPO) is an enzyme that helps your thyroid produce thyroid hormones. The TPOab test detects whether antibodies targeting TPO are present in the blood.
  • Thyroglobulin antibody (TgAb) – Thyroglobulin (Tg) is a protein that helps your thyroid synthesize, store, and release thyroid hormones. A TgAb test will uncover if your body is producing antibodies against thyroglobulin.

If your symptoms suggest an overactive thyroid, the following test can help uncover whether Grave’s disease could be to blame:

  • Thyrotropin receptor antibody (TRAb) – This tests for the antibody that causes your thyroid to be overactive. Considered the “gold standard” for Grave’s disease diagnosis, the TRAb test reduces false negatives and false positives.

Think Your Thyroid Function is Off or Confused? Get Tested and Get Answers

Years ago, if you wanted to get thyroid testing, your only option was to visit an MD. However, times have changed. Nowadays, you can visit a functional medicine practitioner or even order a full thyroid panel yourself online! While the online route is convenient, the drawback is that you may have no clue how to interpret the results. In fact, even your primary care doctor may be unsure how to interpret your results — especially if they’re not well-versed with autoimmunity. That’s where functional medicine comes in. Need some guidance navigating your thyroid testing or treatment options? Click here to set up your complimentary consultation. We’ll chat about your health concerns and develop an individualized plan — so you can stop surviving and start thriving

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