Did you know that an estimated 20 million Americans have some form of thyroid disease?
Among the different types of thyroid disorders, hypothyroidism is the most common. Most of the time, hypothyroidism is mild and causes few (if any) major symptoms.
Left untreated, however, it can worsen over time and lead to other complications with your health.
Is there a history of thyroid disease in your family? Have you noticed symptoms of hypothyroidism in your body? Are you wondering how to test for hypothyroidism?
In this post, we'll briefly discuss some common hypothyroidism symptoms and risk factors. Then we'll reveal 18 different lab tests you can order to test for hypothyroidism.
Read on to learn more—your health depends on it!
What Is Hypothyroidism?
Before we dive into screening and testing, let's first define hypothyroidism.
Your thyroid is a butterfly-shaped gland located in your throat. As one of your body's endocrine glands, it's responsible for producing certain hormones.
Among other functions, your thyroid regulates your metabolism, your heart rate, and your body temperature. If your thyroid isn't active enough to produce the hormones your body needs, these functions will begin to slow down.
When this happens, it's known as hypothyroidism (underactive thyroid).
The symptoms of hypothyroidism vary depending on the severity of the hormonal deficiency. Problems tend to develop very slowly, usually over a number of years.
At first, you may hardly notice the symptoms of hypothyroidism. You may attribute symptoms like fatigue and weight gain to getting older.
But as your metabolism continues to slow down, you may soon develop more obvious problems. Hypothyroidism signs and symptoms may include:
- Increased sensitivity to cold
- Dry skin
- Weight gain
- Puffy face
- Muscle weakness
- Elevated blood cholesterol level
- Muscle aches, tenderness, and stiffness
- Pain, stiffness, or swelling in your joints
- Heavier or irregular menstrual periods
- Thinning hair
- Slowed heart rate
- Impaired memory
- Enlarged thyroid gland (goiter)
Children and teens who develop hypothyroidism generally have the same symptoms as adults. But they may also experience:
- Poor growth, resulting in short stature
- Delayed development of permanent teeth
- Delayed puberty
- Poor mental development
These symptoms are often vague and don't outwardly appear to be related. If you notice some of these symptoms over an extended period of time, it's a good idea to get tested.
The sooner you do, the sooner you can get diagnosed and receive the treatment you need.
Risk Factors for Hypothyroidism
Although anyone can develop hypothyroidism, you're at an increased risk if you:
- Are a woman
- Are older than 60
- Have a family history of thyroid disease
- Have an autoimmune disease, such as type 1 diabetes or celiac disease
- Have been treated with radioactive iodine or anti-thyroid medications
- Received radiation to your neck or upper chest
- Have had thyroid surgery (partial thyroidectomy)
- Have been pregnant or delivered a baby within the past six months
Keep in mind that these are generalizations and that hypothyroidism can affect anyone of any age.
How to Test for Hypothyroidism: 18 Key Lab Tests
Now that you understand hypothyroidism symptoms and risk factors, how do you test for it?
It will likely require a combination of tests to determine your hormone levels and other factors that indicate a thyroid disorder. To make things easier, here's a list of 18 tests you can order to measure how active (or underactive) your thyroid may be.
TSH stands for "thyroid-stimulating hormone." This is the first place to start when you're evaluating the health of your thyroid.
TSH is produced in your pituitary gland inside your brain. This is the "master gland" that controls the level of hormones your thyroid produces and releases into your body.
This test measures how much TSH is in your bloodstream. Normal levels are anywhere between 0.4 and 4.0 milliunits per liter (mU/L). If your TSH levels are too high (over 4.0), it means your thyroid is underactive and could be a sign of hypothyroidism.
2. T3 Reverse, LC/MS/MS
Your body uses part of the T4 thyroid hormone to produce Reverse T3 (rT3). This serves as an inactive form of thyroid hormone.
Reverse T3 may attach to the Free T3 receptors, which slows down your metabolic processes. Some studies suggest that high levels of rT3 can contribute to acute major depressive disorder.
Ordering a Reverse T3 test can help you determine if your body is effectively converting T4 into the proper amount of Free T3 and rT3. Normal levels are below 250 pg/ml (10 to 24 ng/dL).
3. T3 Total
This test measures blood levels of the thyroid hormone T3 (triiodothyronine). Some T3 is directly produced in the thyroid gland, but most T3 is the result of chemical conversion from T4.
Bound T3 attaches to hormones that help to transport it throughout the body. Free T3 circulates through the bloodstream unattached.
A T3 total test measures both the bound and free types of T3 in your body. A normal result range is 100-200 nanograms per deciliter (ng/dL).
4. T3, Free
As mentioned above, there are two types of T3 inside your body. Total T3 may be affected by protein levels and your body's protein binding ability, but the Free T3 hormone is not.
While a Total T3 test measures both types, this test only measures your Free T3 levels. Either test (Free T3 or Total T3) can be used to assess your current hormone levels. The normal range is for Free T3 is 260-480 pg/dL or 4-7.4 pmol/L.
Keep in mind that any of these tests on their own won't be enough to make a diagnosis. By studying your TSH, T4, and T3 levels, your doctor will be able to determine if you have hypothyroidism.
5. T4 (Thyroxine), Total
T4 is the main thyroid hormone your body produces. Also called thyroxine, it plays an important part in regulating your weight, body temperature, metabolism, and mood.
In a healthy thyroid, some T4 also converts into T3 to be used by the body. If you have hypothyroidism, this process can be interrupted. A high TSH level combined with low levels of T4 may signal hypothyroidism.
A Total T4 test is an essential part of assessing and diagnosing an underactive thyroid.
6. T4 Free (FT4)
Approximately 99% of T4 hormones are bound. This means they're attached to proteins that prevent them from entering the body's tissues.
Since most T4 is converted into T3, Free T4 is the more important hormone to measure. Any changes the could indicate hypothyroidism will show up first in T4.
The normal range for Free T4 is 0.8 to 2.8 nanograms per deciliter (ng/dL). You can find out your levels with a T4 Free test.
7. Thyroglobulin Antibodies (TgAb)
One of the most common causes of hypothyroidism is an autoimmune disease known as Hashimoto's.
With Hashimoto's, your body mistakes your healthy, functioning thyroid for a "foreign" invader. It then launches an attack against the thyroid in the form of antibodies.
If you're healthy and your thyroid is functioning normally, you'll have no measurable amount of TgAb in your blood. Elevated levels in a TgAb test are a possible sign of an autoimmune version of hypothyroidism.
8. Thyroid Peroxidase Antibodies (TPO)
Thyroid peroxidase (TPO) is an enzyme found in your thyroid gland. It plays an important role in the normal production of thyroid hormones.
Similar to the thyroglobulin antibodies, there's no reason for your body to produce antibodies against this enzyme. The presence of TPO antibodies in your blood signals an autoimmune attack on your thyroid.
A TPO test detects the level of antibodies against TPO in the blood. The normal range is 0-35 IU/mL.
9. TRAb (TSH Receptor Binding Antibody)
TRAb is an antibody to the thyroid cell receptor for thyroid-stimulating hormone (TSH).
It's found in most patients with Graves' Disease and is a primary cause of hyperthyroidism (overactive thyroid). Normal levels fall between 0.0−1.75 units/L.
What if you have some symptoms that seem hyper and some that seem hypo? This test can help rule out hyperthyroidism and bring you one step closer to the right diagnosis.
10. TSI (Thyroid Stimulating Immunoglobulin)
TSI stands for thyroid-stimulating immunoglobulin. It signals the thyroid gland to swell and release excessive amounts of thyroid hormone into the bloodstream.
TSIs mimic the action of TSH, causing over-secretion of T3 and T4. The TSI level will be abnormally high in persons with hyperthyroidism (Grave's Disease). Normal levels are less than 1.3 or 130%.
A TSI test will measure this hormone in your blood and help your doctor assess your thyroid function.
11. CBC (includes Differential and Platelets)
CBC stands for complete blood count. It's the most commonly ordered blood test to evaluate your overall health.
This test measures the cells that make up your blood, including red and white blood cells as well as hemoglobin, hematocrit, and platelets. Abnormally high or low levels of any of these components can signal an underlying medical condition.
Be sure to include a CBC test with any specific thyroid tests you order. This will provide your doctor with "the whole picture" of what's going on inside your body.
12. Comprehensive Metabolic Panel (CMP)
One of the main symptoms of hypothyroidism is a sluggish metabolism. A CMP test provides vital information about your body's metabolism and chemical balance.
This test measures glucose, electrolytes, calcium, and protein levels in your blood. Like abnormalities in the CBC test, unusually high or low results means your body isn't performing at an optimal level.
The results of this common test can help your doctor determine how fast or slow your metabolism is functioning.
13. Hemoglobin A1c (HgbA1C)
This hemoglobin A1c test reveals your average blood sugar levels over the past few months. It's commonly ordered to help diagnose diabetes.
What does this have to do with thyroid function? Both diseases indicate dysfunction within the endocrine system. Research has found that thyroid disorders can have a major impact on glucose control.
Ordering a HgbA1C test will let you know if your blood sugar is within the normal limits (between 4%-5.6%)
14. Iron and Total Iron Binding Capacity (TIBC)
Diabetes isn't the only disease linked with hypothyroidism.
Anemia is a frequently occurring clinical condition that accompanies thyroid disease. In fact, prolonged iron deficiency can contribute to the development of hypothyroidism.
The TIBC test measures the amount of iron that would appear in blood if all the transferrin were saturated with iron. This reveals if you're anemic, which could facilitate a diagnosis.
15. Lipid Panel with Ratios
Hypothyroidism can contribute to elevated cholesterol levels.
When your body isn't producing enough thyroid hormones, it doesn't have the tools it needs to efficiently break down and remove cholesterol.
A lipid panel test will measure your body's levels of "good" cholesterol (HDL), as well as the "bad" cholesterol (LDL). Higher than normal levels (less than 200 milligrams per deciliter) could signal an underlying thyroid problem.
16. Vitamin D 25-Hydroxyvitamin D (D2, D3)
Hypothyroidism can impair your body's ability to absorb certain vitamins, like Vitamin D.
Over time, low levels of Vitamin D can affect your heart and your bones, reducing your overall bone density.
Check your levels with this Vitamin D test to ensure your levels are where they should be. If they're too low (less than 12 ng/mL), you're Vitamin D deficient and could have hypothyroidism.
17. Vitamin B12 (Cobalamin)
Your B-vitamin levels are another way to determine how well your body is functioning.
In the case of people with hypothyroidism, a Vitamin B12 deficiency often results from gradual damage to the digestive tract. This prevents the absorption of vital nutrients like B-vitamins, which are essential to your wellbeing.
A Vitamin B12 test will reveal if you're within the normal range (200-900 nanograms per milliliter (ng/mL).
18. Vitamin B6 (Pyridoxal Phosphate)
A final test you can take for hypothyroidism is Vitamin B6.
B6 is essential for your body's protein, fat, and carbohydrate metabolism. It also aids in the creation of red blood cells and neurotransmitters.
If you have an underactive thyroid, your body won't absorb B6 as efficiently as it should. This test will determine if your Vitamin B6 levels are normal (5-50 micrograms per liter).
Symptoms of Hypothyroidism? Order Your Tests Today
Hypothyroidism is a common condition with many treatment options available. But first, you have to get diagnosed.
Are you noticing hypothyroidism symptoms? Is there a history of hypothyroidism or other autoimmune diseases in your family? Or do you just feel like something is "off" and you can't quite figure out what it is?
If you answered "Yes" to any of these questions, it's time to take action. Before you can seek hypothyroidism treatment, you need to find out exactly what's happening inside your body.
Keep in mind that test results alone can't prove or diagnose any condition, including hypothyroidism. You'll need to review your results with your doctor before you can receive an official diagnosis and treatment plan.
Now that you know how to test for hypothyroidism, the only thing left to do is get started.
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