Low thyroid function is very common. It is especially common in women. And your doctor may not diagnose you with it because of one simple mistake.
The thyroid controls how quickly the body uses energy, makes proteins, and controls how sensitive the body should be to other hormones. It is exceptionally important. Without thyroid function one cannot survive.
The thyroid is located in the neck just below the Adam’s Apple. The average person should not be able to feel it. It may become enlarged if you have low thyroid function. In that case, one would be able to feel it and it may even be visible in the neck.
The thyroid is controlled by the pituitary gland in the brain. The pituitary secretes a hormone called thyroid stimulating hormone or TSH. TSH tells the thyroid to secrete its hormones. These hormones are called T3 and T4. When these hormones are secreted they make their way back to the pituitary via the blood stream and this tells the pituitary to stop secreting TSH. This is known as a negative feedback loop.
The pituitary secretes TSH which tells the thyroid to secrete its hormone. This hormone then tells the pituitary to stop secreting TSH.
An under active thyroid is known as hypothyroidism. The symptoms are varied and include the following:
- Poor muscle tone (muscle hypotonia)
- Cold intolerance, increased sensitivity to cold
- Muscle cramps and joint pain
- Thin, brittle fingernails
- Coarse hair
- Decreased sweating
- Dry, itchy skin
- Weight gain and water retention
- Bradycardia (low heart rate – fewer than sixty beats per minute)
The most common symptoms I see in practice of low thyroid function are the inability to lose weight and fatigue. Depression is common as well but that can have many causes.
How is the thyroid tested?
The thyroid is tested with a blood test. TSH is generally considered the gold standard to asses thyroid function. A high TSH indicates that the pituitary gland is working too hard to get the thyroid gland to produce its hormone. This means one has hypothyroidism.
I’ve had my TSH tested and it’s normal but I have all the symptoms
This is very common. Unfortunately most doctors do not assess the thyroid completely. There are many other parameters to check besides TSH. Remember TSH is a brain hormone and while it can be valuable it is not the whole picture on the thyroid.
Let’s start with the controversy over the reference levels that most U.S. labs (and therefore doctors) use for a normal TSH. Generally speaking, they use a reference range of 0.5-5.0. If your TSH falls in that range then you are considered healthy, even if you have all of the hypothyroid symptoms. This can be frustrating for many patients. That reference range that most doctors rely on is far too broad and outdated. Unfortunately, medicine is very slow to adapt. This puts the patient at the disadvantage. A more appropriate reference range for TSH is 0.3-3.0. This is a much smaller range and would appropriately diagnose many more people with hypothyroidism.
So, if your doctor uses the old range of 0.5-5.0 and your TSH tested at 4.0 your doctor will tell you that your thyroid is doing just fine and will not treat you. If he were to use the most updated range set forth by the American Academy of Clinical Endocrinologist in 2003 you would be appropriately diagnosed as hypothyroid and be treated accordingly.
What else can be tested?
Remember, TSH is just one parameter to be tested. You can also test for the actual thyroid hormones themselves. When testing for T3 and T4 there are two things to remember. You must test the free and total T3/T4. What’s the difference?
Total T3 and T4 takes into account the total hormone you have. This includes biologically active and inactive forms. The total hormone you have might be normal, but the free hormone might be low.
The free fraction of the hormones can often be low despite a normal total hormone reading. The free hormone is what is actually available to your body to use. It is unbound and biologically active. Think of it like your cash flow. A person might be worth a lot of money with real estate holdings and investments but if they don’t have any actual cash they can’t purchase anything. If you have a low free hormone you will have symptoms of hypothyroidism. However, if it’s not tested it might be missed.
You should also have the anti-thyroid antibodies tested. These are antibodies that some people make their thyroid. The body’s immune system mistakes the thyroid for an invader and begins to attack it. High antibodies alone are enough to cause the symptoms of low thyroid function despite all other parameters being normal.
The bottom line is if you think you might have low thyroid function, don’t rely on just the TSH to tell you. Have the full workup done. That includes:
TSH, free and total T3 and T4 and the anti-thyroid antibodies.
And don’t forget; don’t rely on the outdated TSH scale. Use the smaller more appropriate scale.
Getting an appropriate diagnosis is important and if you use these tips there shouldn’t be any more confusion for you.