You already know that several types of food can affect the results of various blood tests. For example, you shouldn't eat anything for 12-14 hours before a glucose test because any ingested food can increase blood sugar levels and cause an inaccurate diagnosis. Similarly, there are certain rules that you must respect before doing thyroid tests to avoid getting the wrong results.
The thyroid gland is located at the base of your neck and it's responsible for many functions such as stimulating energy production, managing body metabolism, and more. Thyroid tests are necessary to diagnose or monitor a wide variety of diseases. Keep reading to learn more about food and other factors on thyroid tests.
How Food Affects Thyroid Tests
It's important to remember that all the hormones and chemicals in your body are constantly changing. For example, your testosterone levels are at their peak in the morning, and they begin to decline in the afternoon. Similarly, your main thyroid hormones, such as TSH, T4, and T3, are secreted in various quantities at different moments of the day.
If you're ingesting food or any beverages except water, this will impact how thyroid hormones and other hormones in the body are secreted. This is not a good thing because if you do a test in this state, your results might appear incorrect, and you might receive a false diagnosis.
Think about this as if you're the witness of a car accident. If the accident was quite serious, the evidence must be kept in its original state because this is how the authorities will figure out who is the guilty driver. If someone alters the evidence (in our case influences the production of thyroid hormones), the conclusion (diagnosis) of the accident can be misinterpreted.
Finally, you need to know that fasting and postprandial states can affect thyroid hormone results. Fasting refers to not eating anything for 8, 10, or even 12 hours before doing a test—postprandial means doing a test soon after ingesting food. For example, if you do a thyroid test early in the morning in a fasting state, your TSH levels might be higher. This can influence how your subclinical hypothyroidism might be interpreted, as this health problem can be diagnosed solely on TSH levels.
Study on the Effects of Different Nutrients on Thyroid Hormones for Healthy Individuals
Another study performed in 2021 on more than 4,500 individuals shows interesting correlations between different types of foods and their effect on free T3, free T4, and TSH levels. The study participants were from the southern regions of Croatia, and they were split into different groups depending on their health status, gender, lifestyle habits, and more.
More than 58 food items were included in the diet administered to study participants during the testing period. The study results showed that women usually had lower free T3 and free T4 and higher TSH levels than men. At the same time, smokers had lower TSH levels than people who didn't smoke or were ex-smokers.
At the end of the study, researchers concluded that those who consumed a lot of foods with a high glycemic index had a positive association with free T3 and T4 levels while negatively associated with TSH levels. At the same time, foods high in protein or saturated fatty acids showed a negative correlation with free T3 and T4 levels. Another interesting result shows that those with a higher fasting glucose level usually had higher free T4 levels.
Study on the Effects of Food on Thyroid Levels
A study done in 2014 looked at 57 adult patients who had their thyroid hormones measured in a laboratory environment. These patients were split into several groups. The first group had normal T4 and TSH, the second group had increased TSH and normal T4 (subclinical hypothyroidism), and the third group had low T4 and high TSH.
The testing was done in a fasting state two hours after eating a meal. Food choice is not important in this case, as any food can influence thyroid hormones.
The results were impressive. TSH levels were suppressed in all patients after ingesting food regardless of how long they fasted before. T4 levels didn't change enough to make a difference in patients. After the tests were done, almost 75% of the patients could be diagnosed with subclinical hypothyroidism based on the tests done in a fasting state alone. The TSH levels were otherwise within normal ranges in the postprandial tests.
This is an important finding as the time of the day when the test is done, and the fasting/postprandial state can significantly influence a diagnosis of subclinical hypothyroidism, especially for pregnant women.
Other Factors That Could Influence Thyroid Hormone Levels
On top of eating or drinking before a thyroid test, other factors could influence the levels of thyroid hormones. For example, excessive stress can take a toll on your body and cause your hormones to go out of whack, including your thyroid hormones. Although more research is needed to determine how stress can affect you, it's safe to assume that you might not want to take a thyroid test if you're going through a very stressful period.
If a doctor recommends a thyroid test for you, make sure that you're getting enough sleep and normally eat for a few days to get an accurate test result. Sleep deprivation is another factor that could influence the results of your thyroid hormones, especially if you haven't slept at all in 24 hours or more. Dieting to lose weight is known to influence hormonal changes in your body, so you might not want to do a thyroid test if you're sleep deprived or dieting.
Medications Effect on Thyroid Tests
You shouldn't be surprised to find out that different types of drugs can significantly influence the secretion of various thyroid hormones and alter test results. For example, iodine and kelp supplements, Pacerone, chemotherapy drugs, and Lithobid can influence how your thyroid gland produces hormones. You likely need to discontinue these drugs for a few days before doing a thyroid test, but you should only do this at a doctor's recommendation.
Other drugs that could interfere with your thyroid hormone levels include Tyrosine kinase inhibitors and immunomodulating drugs such as Interleukin-2. If you're thinking of doing a thyroid test soon and you take some of these medications, talk with your doctor and see if you have the green light or if you need to adjust/stop your treatment before doing the test.
Effect of Pregnancy on Thyroid Tests
Another thing that could significantly influence thyroid hormones and test results consist of pregnancy. According to the American Thyroid Association, thyroid hormones such as TSH, T3, and T4 vary depending on the pregnancy semester. Doctors should consider this when interpreting thyroid test results for pregnant women.
Effect of Different Types of Diseases on Thyroid Blood Tests
When the body is not well, its hormone production can be drastically affected. Different types of illnesses and diseases can significantly influence thyroid hormone levels and test results. For example, various viral infections and autoimmune disorders such as lupus and Hashimoto's disease can alter your body's levels of thyroid hormones. Make sure that you tell your doctor your medical history and any condition you might have before doing a thyroid test.
What Are the Different Types of Thyroid Tests Available?
You might be happy to find out that there are multiple types of thyroid tests you can do to determine if your thyroid gland is functioning correctly. You can take advantage of individual tests such as the ones that measure your TSH, T3, or T4. However, doctors recommend going for a test panel that incorporates multiple hormones because this provides a clearer picture when it comes to the health of your thyroid gland.
For example, one of the most popular panels checks your TSH, free T3, and free T4 in a single test. It's more affordable and efficient to test your thyroid gland in this manner. Other tests include thyroxine-binding globulin test, comprehensive thyroid panel, which also includes thyroid peroxidase antibody among the other hormones, and reverse T3 test. Ask your doctor for advice if you don't know what type of test is more suitable for you to determine the health of your thyroid gland.
Take Charge- Order Your Thyroid Tests Today!
As you can see, several types of factors can affect the results of your thyroid tests, mainly doing a test in a fasted or postprandial state. With that being said, it's highly recommended that you do thyroid tests regularly to see how your thyroid hormones are working in your body. Follow your doctor's recommendations and pick the right thyroid test for your needs.
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More information about thyroid tests: Thyroid Lab Tests Types and Controversies