By Ken Woliner, M.D., A.B.F.P.
I would like to clarify the tests that one might order to evaluate whether a low thyroid is the cause (or one of the causes) of your symptoms. I will preface the below recommendations based upon what I do in my clinical practice, and that my opinions are not a consensus statement by any means. I am definitely an outlier" and I interpret my laboratory tests more generously than my colleagues. I believe I have sound science to back up my practice pattern, but it doesnt mean that I am 100% right, 100% of the time. Other clinicians may have had other training and other clinical experience, and they may find other diagnostic tests to work better for them. I just seem to get results that I am pleased with (and my patients are pleased with as well).
If you suspect hypothyroidism (underactive thyroid function) you may consider the following methods and tests to help identify this problem:
Complete a questionnaire on hypothyroid symptoms such as the one found in books by Mary Shomons Living Well with Hypothyroidism or Richard and Karilee Shames
Thyroid Power. You may want to bring a completed questionnaire to your physician for his or her review.
Record your underarm basal body temperature with a glass thermometer (not digital). The procedure for doing so is the following:
1. Get a glass thermometer, not digital (the digital ones stop reading after a minute or two and are not as accurate). Non-mercury glass thermometers are now commercially available at Walgreens and other pharmacies (if you have trouble locating a mercury thermometer).
2. Shake down the thermometer the night before you do the test (using your muscles to shake the thermometer will raise your temperature and throw off the test).
Place the thermometer at your bedside with a book (the book will be obvious in a moment).
3. Go to sleep without an extraneous heat source such as a bed partner (spouse, dog, etc), an electric blanket or on a waterbed (they are heated). You are allowed to wear pajamas and use as many blankets as you desire, as they do not throw off the test.
When you wake up in the morning (or if you sleep during the day, when you wake up after at least 4 hours of sleep), use as little movement as possible (all movement moves your muscles and raises your temperature) and place the thermometer in your armpit. Why the armpit? Patients with low thyroid often have allergies or get sinus infections which raise the temperature inside the mouth. Patients rarely get armpit infections, so this site is more reliable. I have had only one patient who had a difference in temperature between armpits, but that was due to unusual anatomy (she had something called an atrial-venous malformation (AVM) in one armpit). Leave it there for at least ten minutes (hence, you have a book to read. J)
4. Women who still have periods should take their temperature over the first 3 days of their period and average the numbers. Women who have had a hysterectomy but still have at least one ovary will probably want to test over a period of 14 days and use the 3 days with the lowest" readings. Men and postmenopausal women can test for any 3 days and average.
5. Normal axillary body temperature is between 97.4 and 98.2 degrees Fahrenheit. Temperatures below that are suggestive of low thyroid.