What is the thyroid?
The thyroid is a small gland located in the lower-front part of your neck. It’s responsible for helping to regulate many of the body’s processes, such as metabolism, energy generation, and mood.
What is a thyroid function test?
Thyroid function tests are a series of blood tests used to measure how well your thyroid gland is working. Available tests include the T3, T4, and TSH.
The thyroid test takes a sample of blood and measures the amount of thyroid stimulating hormone, thyroid peroxidase antibodies, free T3 and free T4 levels.
T4, TSH and Free T4 results
The T4 test and the TSH test are the two most common thyroid function tests. They’re usually ordered together.
- The T4 test is known as the thyroxine test.
- A high level of T4 indicates an overactive thyroid (hyperthyroidism).
- Most of the T4 in your body is bound to protein. A small portion of T4 is not and this is called free T4. Free T4 is the form that is readily available for your body to use.
The TSH test measures the level of thyroid-stimulating hormone in your blood. The TSH has a normal test range between 0.4 and 4.0 milli-international units of hormone per liter of blood (mIU/L).
If you show signs of hypothyroidism and have a TSH reading above 2.0 mIU/L, you’re at risk for progressing to hypothyroidism.
T3 and Free T3 results
The T3 test checks for levels of the hormone triiodothyronine. It’s usually ordered if T4 tests and TSH tests suggest hyperthyroidism. The T3 test may also be ordered if you’re showing signs of an overactive thyroid gland and your T4 and TSH aren’t elevated
The normal range for the T3 is 100–200 nanograms of hormone per deciliter of blood (ng/dL). Abnormally high levels most commonly indicate a condition called Grave’s disease. This is an autoimmune disorder associated with hyperthyroidism.
Your thyroid test will show:
- Normal thyroid function, or
- Hypothyroidism – an underactive thyroid, or
- Hyperthyroidism – an overactive thyroid
Hypothyroidism – an underactive thyroid
If your thyroid gland doesn’t produce enough of these hormones, you may experience symptoms such as weight gain, lack of energy, and depression. This condition is called hypothyroidism, more commonly known as an “underactive thyroid”.
Symptoms of an underactive thyroid
- Being sensitive to cold or feeling the cold more easily
- Weight gain
- Slow movements and thoughts
- Muscle aches, cramps and weakness
- Dry and scaly skin
- Brittle hair and nails
- Loss of libido (sex drive)
- Pain, numbness and a tingling sensation in the hand and fingers (carpal tunnel syndrome)
- Irregular periods or heavy periods
What causes an underactive thyroid?
Most cases of an underactive thyroid are caused by your immune system attacking the thyroid gland and damaging it.
An underactive thyroid can also be the result of treatment for thyroid cancer or treatment for an overactive thyroid (see below).
Treating an underactive thyroid
An underactive thyroid is treated by taking daily hormone replacement tablets called levothyroxine. Levothyroxine replaces the thyroxine hormone, which your thyroid does not make enough of. You will need to take levothyroxine for the rest of your life.
You’ll initially have regular blood tests until the correct dose of levothyroxine is reached. This can take a little while to get right. Once you have found a dose that works for you, you will need to schedule blood tests every year or so.
Hyperthyroidism – an overactive thyroid
If your thyroid gland produces too many hormones, you may experience weight loss, high levels of anxiety, tremors, and a sense of being on a high. This is called hyperthyroidism, more commonly known as an “overactive thyroid”.
Symptoms of an overactive thyroid
- Nervousness, anxiety and irritability
- Mood swings
- Difficulty sleeping
- Persistent tiredness and weakness
- Sensitivity to heat
- Swelling in your neck from an enlarged thyroid gland (goitre)
- An irregular and/or unusually fast heart rate (palpitations)
- Twitching or trembling
- Weight loss
What causes an overactive thyroid?
There are several reasons why your thyroid can become overactive. These include:
- Graves’ disease – a condition where your immune system mistakenly attacks and damages the thyroid (about 3 in every 4 people with an overactive thyroid have Graves’ disease)
- Lumps (nodules) on the thyroid – this extra thyroid tissue can produce thyroid hormones, causing your levels to be too high
- Some medicines such as amiodarone which is used to treat an irregular heartbeat (arrhythmia)
Treating an overactive thyroid
An overactive thyroid (hyperthyroidism) is usually treatable. You’ll usually be referred to a specialist in hormonal conditions (endocrinologist) who will plan your treatment. The main treatments are:
- You may be prescribed medicines called thionamides that are commonly used to treat an overactive thyroid. They stop your thyroid producing excess hormones.
- Radioactive iodine treatment. Radioactive iodine treatment is a type of radiotherapy used to destroy the cells in the thyroid gland, reducing the amount of hormones it can produce. It’s a highly effective treatment that can cure an overactive thyroid. You are given a drink or capsule that contains iodine and a low dose of radiation, which is absorbed by your thyroid. Most people only need a single treatment.
- Occasionally, surgery to remove all or part of your thyroid may be recommended. This may be the best option if:
- your thyroid gland is severely swollen because of a large goitre (swelling in the neck)
- you have severe eye problems caused by an overactive thyroid
- you cannot have other, less invasive treatments
- your symptoms return after trying other treatments
Removing all of the thyroid gland is usually recommended because it stops the symptoms of hyperthyroidism coming back. But you’ll need to take medicine for the rest of your life to make up for not having a thyroid gland. These are the same medicines (usually levothyroxine) that are used to treat an underactive thyroid.
Order a Thyroid Function & Immunity Home Test Kit
Order a Thyroid Function & Immunity Home Test Kit. Get the convenience of home testing with the reassurance of professional clinical analysis. Your results are delivered quickly and securely online.
Thyroid Function & Immunity home blood test kit checks the four key Thyroid Function hormones to give a complete view of your thyroid function and ability to regulate your metabolism.
What’s included in the test kit?
- Gentle fingerprick blood testing kit
- FREE post & packaging
- Results usually within 24 Hours
- Accredited laboratory testing by clinical professionals
- Personalised report with detailed guidance in your online, secure dashboard
- The same accuracy and quality as your GP or hospital
This Thyroid Function & Immunity Test is advised if you:
- suffer from chronic fatigue & tiredness;
- have a low sex drive & loss of libido;
- suffer from depression;
- are experiencing hair loss;
- are overly sensitive to heat or cold;
- experience irregular periods;
- experience poor memory;
- experience tingling or pain in your hands;
- experience unusual tremors;
- find it difficult to sleep properly;
- have a slower than normal pulse (heart rate);
- have had weight gain;
- have had weight loss;
- have higher than normal heart rate;
- have previously had borderline thyroid tests ;
- often feel anxious for no reason;
- struggle to gain weight;
- suffer from constipation;
- suffer from muscle cramps;
- sweat excessively or have a fever;
What is tested?
- FT3. Triiodothyronine (T3) is the one of the two main hormones released by the thyroid gland. It’s role is to regulate your body’s metabolism. This test measures the biologically active unbound form in the blood – Free T3 (FT3). Increased or decreased levels indicate an imbalance and should be interpreted alongside other thyroid markers.
- FT4. Thyroxine (T4) is the most prevalent thyroid hormone produced by the thyroid gland. It is responsible for many vital roles in the body including, metabolism, heart and muscle function, brain development and bone maintenance. Measurement of Free Thyroxine (FT4) is used to assess thyroid health.
- T4. Thyroxine (T4) is a hormone produced by the thyroid gland. It is biologically inactive until it is converted naturally to the active form T3. These hormones are essential for regulating your body’s metabolic rate, heart and digestive functions, muscle control and bone maintenance. Abnormal levels can lead to a huge range of issues and should be investigated further.
- TGAB. Thyroglobulin (TGAB) is a protein produced and used by the thyroid gland to make the thyroid hormones triiodothyronine (T3) and thyroxine (T4). Measuring thyroglobulin helps measure correct thyroid function.
- TPO. If other thyroid tests (FT3, FT4, TSH) indicate disorder with your thyroid, Thioperoxides (TPO) antibodies in your blood suggests that the cause of this could be an autoimmune disorder. This occurs where your immune system makes antibodies that mistakenly attack normal tissue.
- TSH. TSH stands for thyroid stimulating hormone. It’s responsible for regulating your thyroid gland. TSH is made in a gland in the brain called the pituitary. When thyroid levels in your body are low, the pituitary gland makes more TSH. When thyroid levels are high, the pituitary gland makes less TSH. The test also includes advanced antibody testing to indicate if your thyroid is under attack from your immune system. Many thyroid disorders result from an autoimmune disease, so this is an important consideration.