The thyroid is a butterfly-shaped gland which is situated in the front of your neck and wraps around your windpipe. Its job is to produce the hormones which govern metabolism - if excess levels of thyroid hormones are produced your metabolism speeds up which means that many of your bodily functions also speed up. You may be aware of your heart beating faster, of food moving through your digestive tract too quickly leaving you with diarrhoea, of your temperature being raised or you may feel constantly anxious or jittery. This is called hyperthyroidism or, in more familiar terms, an overactive thyroid.
More commonly, the thyroid gland doesn't produce enough thyroid hormones which results in your metabolism slowing down. An underactive thyroid is known as hypothyroidism and a classic symptom is the inability to lose weight. This is certainly a problem with an underactive thyroid but did you know that hair loss, constipation, dry skin and even libido and fertility problems can be attributed to an underactive thyroid?
See our symptoms section for a comprehensive list of symptoms that might be affecting you.
The thyroid gland uses iodine from the food we eat to produce two thyroid hormones: thyroxine (known as T4 because it contains 4 atoms of iodine) and triiodothyronine or T3 (because it has 3 atoms of iodine). Only T3 is biologically active in our cells (controlling metabolism, the process which converts oxygen and calories to energy) which means that T4 must be converted to T3 before your body can use it.
Thyroid hormone production is governed by the pituitary gland which is situated at the base of your brain. It receives information about the amount of T4 and T3 circulating in your bloodstream and, if levels are low, releases thyroid stimulating hormone (TSH) to stimulate the thyroid gland to produce more. A blood test to measure TSH is often used to determine thyroid activity - a low TSH reading signals that thyroid hormones are elevated whereas a raised TSH result could mean that your thyroid gland is struggling to produce the required levels of hormones. Many experts believe that a TSH reading on its own is not sufficient to make a diagnosis of thyroid disease, and that a more comprehensive picture is obtained from blood tests which include T4 (total and free), free T3 as well as thyroid antibodies.
So what goes wrong?
Thyroid problems can occur if at any stage of the process something goes wrong; for example, if the pituitary gland fails then it will not release enough TSH to regulate thyroid production or if you don't consume enough iodine in your diet (not a common problem in the UK) then your thyroid may be unable to produce sufficient amounts of thyroid hormones. A common cause of thyroid disorders is autoimmune disease which is a disorder of the immune system. Instead of attacking "foreign" invaders, your immune system mistakes your own cells as "foreign" and begins attacking them instead. Autoimmune diseases are common and range from psoriasis, rheumatoid arthritis, lupus, coeliac disease and multiple sclerosis. If you or a close family member suffers from an autoimmune disease this raises your risk of thyroid disease.
Hashimoto's thyroiditis or Hashimoto's disease is the name given to an underactive thyroid caused by an autoimmune disorder. In this case your immune system attacks the cells of the thyroid gland leaving them unable to produce thyroid hormones.
Graves' disease is the name given to an overactive thyroid caused by an autoimmune disorder. In this case, the immune system creates antibodies which the thyroid gland responds to by producing excess levels of thyroid hormones.
Other problems can result from the poor conversion of T4 to T3 or because of stress which causes your body to deliberately slow your metabolism. Whatever the problem, blood tests can help to find the answer.
Getting a diagnosis
For many people a simple blood test for TSH and free T4 can lead to a diagnosis of thyroid disease. For others, however, getting a diagnosis can be more difficult. Sometimes blood test results are within the normal range but symptoms persist. This is why it is often important to dig deeper to find out what might be causing your symptoms. We've created profiles which include tests for the key thyroid hormones as well as important nutritional tests; we've made all the thyroid hormones available as single tests; and we've included a long list of vitamins and minerals which may affect your thyroid function.
For many people a thyroid disorder can be treated very easily and simply either by replacing thyroid hormones or by taking anti-thyroid medication. For others, getting the right balance of hormones is a long process of trial and error until they get the right medication and dosage to relieve their symptoms. Thyroid function tests are especially important in this process to monitor how your thyroid hormone levels are responding to treatment. Our monitoring profiles are designed to give you important information about your hormone status during treatment.