My Results Have Come Negative For Underactive Thyroid? Could They Be Wrong?
Although there's every chance you may not have an under-active thyroid, equally you may have a poor performing thyroid, but the test failed to diagnose it.
Setting this misconception straight may be slightly controversial but with any luck it will help to enlighten people with suspected hypothyroidism that their test results could be inaccurate.
The thyroid gland is situated at the front of the neck and is responsible for a number of essential bodily functions, including controlling the metabolism, the maintenance of bodyweight and the internal regulation of temperature. People suffering from an under-active thyroid (hypothyroidism) can develop a wide range of symptoms including tiredness, weight gain, water retention and an intolerance to the cold, which can quite easily go undetected and be put down to ‘stress' or a ‘hectic lifestyle'. It's because of its subtle symptoms that hypothyroidism is so difficult to diagnose and trying to persuade your doctor that something is not quite right is sometimes very difficult. Thankfully, in recent years hypothyroidism has been recognised as a fairly common problem, especially in women, and GPs are far more willing to send you off for an investigative blood test.
If you suspect you have an under-active thyroid and your doctor agrees to give you a blood test, that's one battle won. If the test results are negative, however, you may have a fight on your hands to prove that your thyroid function could still be well below what it should be. The reason for the ambiguity of the blood test is down to the test itself. Unless you have a very understanding doctor, your blood will be tested for Thyroid Stimulating Hormone (TSH). This test is as cheap as chips and has been the standard since the seventies, but as medical science has evolved, its limitations and inaccuracy have come to light.
TSH is produced by the pituitary gland and regulates the thyroid. Put simply, if the thyroid is performing as it should, only a trickle of TSH is required to stimulate the thyroid gland to produce sufficient quantities of hormones.
However, if the thyroid gland under-performs, then the production of TSH is increased in an effort to stimulate the thyroid to produce more hormones. Therefore, when you are tested for a under-active thyroid, your results will come back as a figure indicating your level of TSH.
Depending on the value of this figure, you will classed as within ‘normal' range, meaning you have been given the all-clear, or you may fall into the ‘abnormal' range, which means it is likely that medication will be prescribed for a sluggish thyroid.
The serious flaw in this method of hypothyroidism diagnosis is the interpretation of ‘normal'. ‘Normal' range varies depending on the country you are in, and how competent and knowledgeable your GP is about the thyroid test. According to the organisation Thyroid UK, the supposedly ‘normal' range of your TSH in the UK is approximately 0.4-4.5. In the US it is 0.4-2.5.
Like the BMI test, some doctors will look at your reading and cross-reference it with what is regarded as ‘normal' and bingo: ‘Mrs Jones, your reading is normal, therefore you do not have an under-active thyroid (although you have all the symptoms), so try getting some rest.' The question is, what if Mrs Jones' TSH reading was 4.4? Just 0.1 higher and she would have been diagnosed with hypothyroidism and much-needed medication in the form of thyroxin would be prescribed. This is a common scenario and unfortunately so many cases of this debilitating disease go undiagnosed every year for this very reason. ‘Normal' may be deemed normal, but only just.
Thankfully, if you or anyone you know has experienced something like this then help is at hand. First, you are fully entitled to find out what your TSH level is, so call your doctor and get the results. Second, it's always worth asking if you can have another type of thyroid test, which tests for the level of hormones - known as T3 and T4 - your actual thyroid secretes.
Visit the Thyroid UK website at www.thyroid-uk.org for more information about the disease.