Are you overweight? Are you saying to yourself, "I feel cold all the time" when everyone else is comfortable? Are you sleeping more and more and still waking up tired? Do you feel sluggish and achy even when you have not done anything strenuous? Are you having constipation or feeling depressed for no reason? Do you have straw for hair or are you losing your hair? Is your skin dry and scaley?
The most commonly ordered tests for evaluating these symptoms are tests for thyroid hormones, usually TSH or T4. If the test comes back low, the patient is diagnosed with hypothyroidism and usually started on Synthroid therapy. Oftentimes however, the thyroid tests come back normal or "borderline low". The patient may be given a prescription for thyroid medication just in case it might help.
Other times the patient is told that they are just depressed and should see a therapist for counseling. Many times they are offered a prescription for an anti-depressant medication. Other patients are told that they are "just getting older" and just need to accept the fact that they are not going to feel as well as they used to feel.
When the patient has known hypothyroidism and is already on thyroid medications, if he develops any of the above symptoms, the patient often assumes that he needs more thyroid medication and insists that his doctor prescribe a higher dose of thyroid medicine. This response is reinforced by the fact that often the patient does feel better with the increased dose-- at least for a few weeks -- but then the symptoms come back. This scenario may be repeated many times until lab tests are eventually done which often show very high levels of thyroid. At this point, the patient's dose is decreased and then they feel terrible on doses of thyroid that show normal lab results. If the patient is truly hypothyroid, when they are started on thyroid medicine, the symptoms do not come back a few weeks later.
What is really going on in these situations? Does a person need to settle for having these symptoms just because they are getting older? Absolutely not!
First of all, the above symptoms are very common and may occur in many other endocrine disorders sometimes due to subtle deficiency of testosterone, estrogen, growth hormone and/or adrenal hormones. A patient with known hypothyroidism may develop a second endocrine deficiency, for example, menopause which can mimic some of these symptoms. If the thyroid tests are truly low, then of course the person should be treated with some form of thyroid replacement. However, if the tests are not low, rather than taking thyroid medicine that they probably don't need, they should undergo a definitive endocrine evaluation to determine the true cause of their symptoms.
Another factor, which may explain a discrepancy between thyroid tests and symptoms, is related to the particular thyroid hormone, which has been tested. The predominant hormone, which is produced by the thyroid gland, is T4 but T4 is primarily a storage form of thyroid hormone, which circulates throughout the blood stream. When the tissues get ready to actually utilize thyroid for cellular metabolism, the T4 must be converted to T3.
Some individuals may have normal amounts of T4 in their blood but they are unable to convert the T4 to T3, which is the active metabolite. In addition, it is more accurate to test for free T4 and free T3 which enables the physician to see the hormone that is truly available to the tissues instead of that bound up to the carrier protein.
In a study in patients with hypothyroidism, a combination of T4 and T3 was more effective than T4 at relieving symptoms of hypothyroidism in two-thirds of the patients (New England J. Med 340:424, Feb 11,1999). There are many prescription preparations available, which enable the physician to give a combination of these two hormones for those patients who have problems with this conversion.
In a general practice setting, patients are usually tested only with a TSH and occasionally with a T4 blood test, which of course, will not pick up problems with T3. Interestingly, this problem with poor conversion from T4 to T3 may not necessarily be a permanent genetic problem. Rather it may be related to nutritional deficiencies in selenium and/or zinc and will often improve with correction of these deficiencies.
So in summary, because the symptoms that occur with hypothyroidism can be similar to other endocrine deficiency diseases, it is important that an appropriate diagnosis be established. It is much better to treat the cause of the symptoms instead of resorting to medications that merely cover up the symptoms only to have them recur weeks later.