Tuli Health - Thyroid Test


Thyroid Test

What Is the Thyroid Gland?

The thyroid gland is a butterfly-shaped endocrine gland that is normally located in the lower front of the neck. The thyroid’s job is to make thyroid hormones, which are secreted into the blood and then carried to every tissue in the body. Thyroid hormones help the body use energy, stay warm and keep the brain, heart, muscles, and other organs working as they should.

The major thyroid hormone secreted by the thyroid gland is thyroxine, also called T4 because it contains four iodine atoms. To exert its effects, T4 is converted to triiodothyronine (T3) by the removal of an iodine atom. This occurs mainly in the liver and in certain tissues where T3 acts, such as in the brain. The amount of T4 produced by the thyroid gland is controlled by another hormone, which is made in the pituitary gland located at the base of the brain, called thyroid stimulating hormone (abbreviated TSH).

For the most part, the symptoms of thyroid disease can be divided into two groups — those related to having too much thyroid hormone (hyperthyroidism) and those related to having too little thyroid hormone (hypothyroidism).


Hypothyroidism (known as underactive thyroid) is a condition of thyroid hormone deficiency and is usually caused by autoimmune Hashimoto's thyroiditis.

Hypothyroidism is found in about 2% of the UK population and in more than 5% of those over 60. Women are 5 to 10 times more likely to be affected than men. Long-term consequences of hypothyroidism include cardiovascular disease and an increase in cardiovascular risk factors, including hypercholesterolaemia.

In hypothyroidism, the thyroid gland does not produce sufficient thyroxine, so the T4 and T3 levels are low. This causes an increase in TSH to try and stimulate the thyroid to produce more thyroxine.

Signs and Symptoms of Hypothyroidism

The signs and symptoms of hypothyroidism vary, depending on the severity of the hormone deficiency. Problems tend to develop slowly, often over a number of years.

Hypothyroidism signs and symptoms may include:

  • Fatigue and sluggishness
  • Increased sensitivity to cold
  • Constipation
  • Dry skin
  • Weight gain
  • Puffy face
  • Having a hoarse voice
  • Muscle weakness
  • Elevated blood cholesterol level
  • Muscle aches, tenderness and stiffness
  • Pain, stiffness or swelling in your joints
  • Heavier than normal or irregular menstrual periods
  • Thinning hair
  • Slowed heart rate
  • Depression
  • Impaired memory
  • Enlarged thyroid gland (goitre)

Hypothyroidism can become a serious and life-threatening medical condition if you do not get treatment from a healthcare provider. If you are not treated, your symptoms can become more severe.


Hyperthyroidism (known as overactive thyroid) is when the thyroid gland produces too much thyroid hormone. In hyperthyroidism the thyroid gland produces too much thyroxine, so the T4 levels are high. This causes a decrease in TSH to try and stop the thyroid producing more thyroxine.

In the UK, autoimmune hyperthyroidism (Graves' disease) is the most common form, accounting for 60 to 80% of cases. Thyrotoxicosis is a common endocrine disorder with a prevalence of around 2% in UK women and 0.2% in men.

Signs and Symptoms of hyperthyroidism

  • Include heat intolerance
  • Unexplained weight loss
  • Rapid heartbeat
  • Nervousness
  • Insomnia
  • Breathlessness
  • Fast heart rate
  • Anxiety
  • Hand tremors

What Does the Thyroid Function Test Measures?

The thyroid tests are used to evaluate the function of the thyroid gland; to help diagnose thyroid gland disorders. The thyroid hormones regulate the body’s metabolism and how it grows, functions and uses energy.

As mentioned, the thyroid gland is located at the front of the neck. It secretes two hormones known as thyroxine (T4) and tri-iodothyronine (T3). The release of T4 and T3 into the blood is controlled by a third hormone called Thyroid Stimulating Hormone (TSH), this hormone is responsible for keeping FT4 and FT3 at the right levels. Collectively, these three hormones are referred to as ‘Thyroid Function Tests’ (TFTs).


  • TSH
  • T4
  • T3
  • TSH

Thyroid Stimulating Hormone (TSH), is a hormone that regulates the release of hormones from your thyroid. These hormones, T3 and T4, help control growth and metabolism. A TSH test can check for hyperthyroidism or hypothyroidism.

The best way to initially test thyroid function is to measure the TSH level in a blood sample. Changes in TSH can serve as an “early warning system” – often occurring before the actual level of thyroid hormones in the body becomes too high or too low. A high TSH level indicates that the thyroid gland is not making enough thyroid hormone (primary hypothyroidism). The opposite situation, in which the TSH level is low, usually indicates that the thyroid is producing too much thyroid hormone (hyperthyroidism).

Occasionally, a low TSH may result from an abnormality in the pituitary gland, which prevents it from making enough TSH to stimulate the thyroid (secondary hypothyroidism). In most healthy individuals, a normal TSH value means that the thyroid is functioning properly.


Thyroxine (T4) is the main hormone produced by your thyroid. It plays an essential role in regulating the energy your body uses. Free T4 measures the amount of T4 that's available for your body to use. This test can help check for hyperthyroidism or hypothyroidism.

A Free T4 measures what is not bound and able to enter and affect the body tissues. Tests measuring free T4 more accurately reflect how the thyroid gland is functioning when checked with a TSH.


Triiodothyronine (T3) tests help diagnose hyperthyroidism or to show the severity of hyperthyroidism. Low T3 levels can be observed in hypothyroidism, but more often this test is useful in the diagnosis and management of hyperthyroidism, where T3 levels are elevated.

Free T3 or free triiodothyronine is a method of measuring T3 that eliminates the effect of proteins that naturally bind T3 and may prevent accurate measurement.

Who Is This Test For?

People who may benefit from having a thyroid function test include:

Individuals who are concerned that they may have a thyroid problem and those who wish to monitor a previously diagnosed condition.

Early signs and symptoms of thyroid dysfunction may often be very non-specific. Because these symptoms could result from any number of disorders, it's important to see your health care provider as soon as possible for a timely and accurate diagnosis.

How Do I Order My Thyroid Test?

Thyroid blood test requires a small blood sample(finger-prick) and makes checking your thyroid levels privately, fast, affordable, and convenient. All you need to do is collect your sample and send it directly to Tuli accredited lab for analysis. Accurate results will be available within 2 working days of receipt of your sample in the laboratory.

Do I Need to Do Anything Before My Test?

Thyroid blood tests may give false results if you're taking biotin, a B vitamin supplement that may also be found in multivitamins. To ensure an accurate test, stop taking biotin at least 48 hours before blood is taken.

What Will the Result Show?

Our thyroid function test will report your levels for TSH, FT4 and FT3 with comments if result is normal or abnormal with suggestions of whether you need to discuss the results with a healthcare professional or not.

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