Dr. Jacqueline Gerhart: More Than One Test For Hypothyroidism
Madison, Wisconsin - UW Health Family Medicine physician Jacqueline Gerhart writes a column that usually appears weekly on madison.com and in the Wisconsin State Journal. Columns are re-published here with permission.
Dear Dr. Gerhart: I'm positive I'm hypothyroid. I have all the symptoms: weight gain, fatigue, hair falling out, constipation, dry skin, etc. But, my doctor keeps telling me that my thyroid test is normal. Are those tests really accurate?
Dear Reader: Yes, the tests that we have for diagnosing hypothyroidism are accurate. But be sure to discuss with your doctor what type of thyroid tests were done. The most common blood test to screen for thyroid disorders is called the TSH. But you should be aware that the TSH - or thyroid stimulating hormone - is actually not made by the thyroid. It is part of a complex cycle of hormones in your brain that helps regulate your thyroid and your body's metabolism.
Usually when people say they are hypothyroid, they are referring to having a low "free T4" hormone. T4 is a hormone that is produced by the thyroid. Usually a physician will check your TSH level first, and if that level is abnormal, then he or she will check your "free T4" level. Some types of T4 are "bound," or not active. The "free T4" is the active hormone that is available to your body. In addition to T4, the thyroid also produces a hormone called T3. This one is less commonly tested, since its levels are 10 times lower in the blood than T4 levels. And a low T3 alone doesn't reliably diagnose hypothyroidism. In fact patients without thyroid disease may have a low T3 level, and people with hypothyroidism can have normal T3 levels. So, TSH and T4 are the best predictors of hypothyroidism for most people.
Most patients who are hypothyroid start a medication called levothyroxine. This is a synthetic form of T4. Essentially it adds T4 to your body to bring up your thyroid levels. Some patients prefer to use "natural thyroid hormone" derived from desiccated animal thyroids. Some of these contain T4 and a bit of T3 - often in a ratio of 4 to 1. However, these formulations are less popular because they can vary in their potency and only some of them are FDA approved.
So, you have been told you are not hypothyroid but have the symptoms? First go to your primary care physician for a history, physical and to discuss your lab results.
Thyroid disease is common - about 20 million Americans have a thyroid condition - so primary care physicians are quite familiar with it. Yet, not everything that seems to be a thyroid problem is actually a thyroid problem. Sometimes thyroid symptoms can be mistaken for depression, menopause, generalized decreased metabolism (such as from age, or lack of physical activity), or other hormone or vitamin deficiencies.
This column provides general health information and is not specific advice intended for any particular individual(s). It is not a professional medical opinion or a diagnosis. Always consult your personal health care provider about your concerns. No ongoing relationship of any sort (including but not limited to any form of professional relationship) is implied or offered by Dr. Gerhart to people submitting questions.
Date Published: 11/06/2013