1. Thyroid Function Tests [Internet]. Lab Tests Online UK - Association for Clinical Biochemistry and Laboratory Medicine. 2019 [cited 29 June 2021]. Available from: https://labtestsonline.org.uk/tests/thyroid-function-tests#:~:text=Currently%2C%20the%20majority%20of%20UK,the%20bridge%20of%20your%20nose.

2. Thyroid function tests - a complete guide [Internet]. British Thyroid Foundation. 2021 [cited 29 June 2021]. Available from: https://www.btf-thyroid.org/thyroid-function-tests

3. Underactive thyroid (hypothyroidism) [Internet]. National Health Service - UK. 2020 [cited 29 June 2021]. Available from: https://www.nhs.uk/conditions/underactive-thyroid-hypothyroidism/diagnosis/

4. Hyperthyroidism [Internet]. Thyroid UK. 2021 [cited 29 June 2021]. Available from: https://thyroiduk.org/if-you-are-hyperthyroid/

5. Current BTA guidelines and statements [Internet]. British Thyroid Association. 2021 [cited 29 June 2021]. Available from: https://www.british-thyroid-association.org/current-bta-guidelines-and-statements

6. Thyroid disease: assessment and management [Internet]. National Institute for Health and Care Excellence. 2019 [cited 29 June 2021]. Available from: https://www.nice.org.uk/guidance/ng145/chapter/Context

7. Favresse J, Burlacu M, Maiter D, Gruson D. Interferences With Thyroid Function Immunoassays: Clinical Implications and Detection Algorithm. Endocrine Reviews. 2018;39(5):830-850.

8. Sheehan M. Biochemical Testing of the Thyroid: TSH is the Best and, Oftentimes, Only Test Needed – A Review for Primary Care. Clinical Medicine & Research. 2016;14(2):83-92.

9. Esfandiari N, Papaleontiou M. Biochemical Testing in Thyroid Disorders. Endocrinology and Metabolism Clinics of North America. 2017;46(3):631-648.

10. Danzi S, Klein I. Amiodarone-Induced Thyroid Dysfunction. Journal of Intensive Care Medicine. 2013;30(4):179-185

Following a healthy and balanced diet is essential in keeping your thyroid function healthy. You should also make sure that you eat enough antioxidant-rich food like nuts and berries and try to avoid gluten and starvation diets.

If you are pregnant or/and have type 1 diabetes, you should pay extra attention to your diet and get tested for thyroid functions regularly. In fact, these conditions can increase the risk of thyroid disease.

Sleep patterns also play an important role in maintaining your thyroid healthy. One study showed that if you sleep too little (less than 7 hours per day) or too much (more than 8 hours per day), you might be at a higher risk of developing thyroid problems. Having healthy sleep patterns also help you maintain a healthy immune system, which in turn helps you keep your thyroid healthy.
 

As with an underactive thyroid, an overactive thyroid (hyperthyroidism) can cause different symptoms based on the person and the level of activity of the gland. 

The most common symptoms are weight loss; increased appetite; rapid and irregular heartbeat; anxiety; irritability; trembling of hands and fingers; diarrhoea; nausea; vomiting; excessive sweating; low tolerance to heat; thinning of the skin; swollen neck; development of breasts in men; itching; hair loss; insomnia; and urinating more frequently.

If left untreated, an overactive thyroid can cause serious health problems such as thinning of bones, vision loss, a higher risk of heart disease, and fertility problems.
 

The signs and symptoms of an underactive thyroid (hypothyroidism) usually develop over a long period of time and depend on the amount of thyroid hormones produced. Symptoms can also vary from person to person depending on their overall health. 

The most common symptoms include fatigue; weight gain; low tolerance to cold; dry skin; depression; constipation; slow heart rate; puffy face; muscle weakness and cramps; high cholesterol levels; impaired memory; stiffness and swelling of joints; irregular menstrual periods; thinning hair; swollen neck; frequent respiratory and urinary infections; insomnia; anaemia; and loss of sexual drive. 

If left untreated, an underactive thyroid can cause more severe symptoms such as hearing loss; hoarseness; and an even slower heart rate which can increase the risk of heart disease.

In infants, common signs and symptoms of an underactive thyroid include yellowness of the skin and the whites of the eyes; a larger than average tongue; difficulty breathing; an umbilical hernia; and excessive crying. 
 

•    TSH: 0.27 to 4.2 mU/L (milliunits per litre)
•    FT4 (free T4): 12.0 to 22.0 pmol/L (picomoles per litre)
•    FT3 (free T3): 3.1 to 6.8 pmol/l (picomoles per litre)

Note that normal ranges will vary between laboratories, and may be amended over time.

Keep in mind that certain medications, pregnancy, and age are all factors that can influence your test results.
 

A thyroid function blood test measures the amount of free thyroid hormones (not linked to proteins) and TSH in your bloodstream. 

The results of your thyroid function test can tell you if your thyroid function is normal or if you have results consistent with primary hypothyroidism, subclinical hypothyroidism, hyperthyroidism, or subclinical hyperthyroidism. 

Having a high level of TSH means that your thyroid is underactive (hypothyroidism). If you have normal values of thyroid hormones with high levels of TSH, you may have subclinical hypothyroidism, which means you are at an early stage of the progression of the disease, and this is why you probably are not showing any signs or symptoms. If on the other hand, the thyroid hormone values are lower, it could be that you have primary hypothyroidism, which is at a more advanced stage compared to subclinical hypothyroidism.

Low levels of TSH indicate that your thyroid is overactive (hyperthyroidism). As with the underactive thyroid, having low levels of TSH with normal thyroid hormone levels means that you can have subclinical hyperthyroidism, whereas if you had higher levels of thyroid hormones, it probably means you have hyperthyroidism. 

The Vitall thyroid function with automimmunity blood test can also measure the levels of specific antibodies that are directed at the thyroid gland or hormones. The results of these tests are used to diagnose thyroid auto-immune diseases, a case in which your body's own immune system attacks your thyroid gland or hormones.
 

The thyroid gland mainly produces two hormones: triiodothyronine (T3) and thyroxine (T4). Most T4 is converted to T3, which is the active hormone. T3 and T4 play an important role in regulating your heartbeat, brain health, skin dryness, breathing, weight, metabolism, growth, sexual functions, mood, and many other body functions. 

The production of these two hormones by the thyroid gland is controlled by the thyroid-stimulating hormone (TSH) which is released from the pituitary gland, a pea-shaped organ situated just below your brain. TSH production in turn depends on the amount of T3 and T4 in the bloodstream. This system creates the balance that your body needs to function optimally.
 

If you recognize any of the symptoms mentioned above, you should talk to your GP who may then ask you to take the thyroid test. You can also take a thyroid test at home to check whether your thyroid hormone levels are in the normal range.

If you are diagnosed with an underactive thyroid (hypothyroidism), you should take the thyroid test once a year. If you are diagnosed with an overactive thyroid (hyperthyroidism), you should get tested every month at the beginning of the treatment and then less frequently as the medications begin to work. If your doctor changes your thyroid treatment, you should take the thyroid test after 2 months to measure the effects of the regimen change.

If you have no symptoms of hypothyroidism and your TSH is borderline high in 2 consecutive tests, your thyroid peroxidase antibodies test results will determine how often you need to do the regular check-ups.

The moment you take a thyroid test is very important because it all depends on whether you are undergoing other treatments on the side.

Anyone who is prescribed amiodarone must take the thyroid test before starting their treatment. You should take follow-up tests every 6 months in the beginning and then every 12 months.

If you take biotin supplements, you might need to wait 8 hours after the last dose to take the thyroid test.

Lithium can also affect thyroid function, so if you take this drug, you should get tested at least every 6 months.

Studies have shown that TSH levels peak during menstrual periods, so this is another factor to consider when getting your thyroid function tested.  

There are no real restrictions in terms of eating before taking the thyroid test, in fact, it is highly recommended to eat before the test as fasting can influence your TSH levels.
 

The thyroid gland is a small butterfly-shaped organ that is located just below the Adam’s apple at the front of your neck.

If you have an underactive thyroid (hypothyroidism), adapting your diet can be very beneficial. With an underactive thyroid, your body needs more thyroid hormones (T3 and T4) to function properly. 

There are three elements that can help your thyroid to produce more hormones: iodine, selenium, and zinc.

Iodine is the building block of thyroid hormones T3 and T4, so reasonably increasing its intake can help your body. Seafood, such as fish, seaweed, and shrimp, is a good source of iodine. Dairy products (milk, yogurt, and cheese) and eggs are also good sources of iodine. Most table salt in the UK is iodized, which also makes it a practical source of iodine. Be careful not to consume too much iodine-rich food however, because it can lead to an overactive thyroid. 

Selenium plays a very important role in maintaining healthy thyroid hormone levels. It helps convert T4 into T3, the active form of the thyroid hormone. Important sources of selenium are nuts, cereals, grains, breads, eggs, seafood, chicken, and beef. 

Zinc not only helps the conversion of T4 into T3, but it also helps you maintain healthy levels of TSH. Shellfish, beef, chicken, beans, and nuts are good natural sources of zinc. Iodine and selenium supplements are also available on the market, but it is better to consult your physician before taking any.

On the other hand, if you have an overactive thyroid, you should eat food that is low in iodine such as non-iodized salt, honey, fruits, homemade breads, oats, potatoes, and unsalted nuts. Cruciferous vegetables like broccoli, brussels sprouts, cauliflower, kale, and bamboo shoots reduce the amount of iodine your thyroid uses, which can decrease the amount of thyroid hormones that are produced. 

Iron is another mineral that plays an important role in maintaining your thyroid healthy, in fact, studies have shown that people with an overactive thyroid had low levels of iron. Good sources of iron are red meat, poultry, seeds, whole grains, and green vegetables. It may seem counterintuitive, but food rich in selenium and zinc can also help you if you have an overactive thyroid. They ultimately help your thyroid gland regulate its activity.

Taking a home thyroid function test is very important because the health of your thyroid will affect almost every aspect of your bodily functions and organs, from your heart to your weight, brain function, muscle development, and lungs to only name a few. 

An early understanding of thyroid problems is always beneficial because it can help contain the extent of the problem, which is why you should get tested regularly, especially if you take certain medications or have specific medical conditions that might affect the activity of your thyroid gland. 
 

The thyroid function and autoimmunity home test kit is also available to measure the levels of specific antibodies that are directed at the thyroid gland or hormones in auto-immune diseases.