Testing Your Thyroid
The good news is that there is a simple blood test that can measure thyroid function to determine whether or not your hormone production is normal (the "gold standard" is to test one of many thyroid functions, which is the production of thyroid stimulating hormone). The bad news is that if you get five doctors in a room, you'll get five different opinions on what is "normal" and what is not. In my practice, I don't rely on blood tests alone because over the years I have found that what is normal for one person, and even normal for the population at large, may be abnormal for someone else. I use other tests as well (such as one that tests for particular antibodies) and palpation (examining with my hands) of the thyroid to determine its size, shape, firmness, or location to check for abnormalities. Internists may do this as well, but since they do not palpate the gland as frequently as endocrinologists do, they may miss the diagnosis. Some doctors may recommend an ultrasound of the thyroid as well.
Here's where the tricky part comes in. As of 2010, at most laboratories in the United States, the official normal reference range for the thyroid stimulating hormone blood test runs from approximately .5 to 5.0 (measured in micrograms per deciliter). Reference range is what determines—for the vast majority of physicians, who rely on blood tests almost exclusively—whether or not thyroid disease is even diagnosed at all, much less treated, and when diagnosed, how it is treated. In January of 2003, the American Association of Clinical Endocrinologists recommended that doctors "consider treatment for patients who test outside the boundaries of a narrower margin based on a target TSH level of 0.3 to 3.0." Even though many years have passed since the new range was established, some doctors use it and some don't. The issue that it raises is this: One study found that using a TSH upper normal range of 5.0, approximately 5 percent of the population is hypothyroid. However, if you use 3.0 as the top of the normal range, approximately 20 percent of the population would be hypothyroid. That means that millions of patients with hypothyroidism are being undiagnosed and untreated.
There are now more effective blood tests that provide a complete picture of how well the thyroid produces T4, how well the body converts T4 into T3, how much of the active form T3 is created, and whether there are significant anti-thyroid antibodies present. A complete panel would also include levels of free (unbound) T3 and T4. You might want to suggest to your doctor that she use the free T3 and T4, as the "regular" T3 and T4 totals may not be as accurate.
One of the problems with thyroid testing is that they are typically not on the list of things that are regularly checked in a standard or even a more comprehensive blood test panel. Just like the guidelines we have established for testing for colon cancer, for instance, beginning at age 50 and not before, it's not until you reach the age of 65 that your doctor will routinely request thyroid testing.
When you complain to your doctor about putting on weight, losing a little hair, fatigue, lack of libido—most of the time you get the same response: "Well, you are getting older, it's to be expected." If you are suffering from any of these symptoms and your doctor doesn't suggest testing, bring it up yourself. Most doctors, even though they may be skeptical, will order the testing if you insist.
I Keep Forgetting What You Said About Thyroids…
Here is a frightening thought: many doctors have diagnosed patients with dementia and Alzheimer's disease, when in reality what they had was a thyroid disorder. A 2008 study published in the Archives of Internal Medicine found that older women who had levels of TSH that were either too high or too low had more than twice the risk of Alzheimer's disease than those with more moderate levels (the same was not true of men). This is another reason that testing your thyroid become part of your standard testing routine as you get older!
Your Numbers, Your Doctor, and You
Here's an important point to remember if do get tested and your numbers are not "normal." Hypothyroidism has a huge range, from very mild to quite severe. Not only that, one person whose TSH tests result in a reading of 2.5 may feel perfectly fine, while another person with the same reading may be suffering a battery of symptoms. The numbers and the symptoms don't always correlate. Most of the time, taking thyroid medication will cure your symptoms and you will feel better within a matter of days; by six weeks on the medication you'll have a very good idea of how it's working. Unless you tell your doctor how you're feeling, he or she has nothing to go on but your test results. You need to share with your doctor if your symptoms are getting better (or worse), and you need to be consistently retested to see how your medication is working. Your numbers may go back to normal, but if you're still not feeling well it's your responsibility to tell your doctor so that more tests can be taken or your medication can be tweaked until you find what works best for you.
It is possible, however, to go overboard with thyroid medication. Some of my patients have the "if some is good, more is better" attitude. However, too much thyroid medication can stress out the adrenal glands, which will then overproduce cortisol as well as dysregulate (impair) the ratio of cortisol and DHEA and epinephrine and norepinephrine. This will leave you more fatigued than you were in the first place, because the rest of your body's systems will not be able to produce the energy needed to keep up with your now revved-up thyroid.
Iodine Deficiency and the Thyroid
Since iodine is needed for the production of thyroid hormone, and the body does not make iodine, we have to get through what we eat. It is commonly found in foods such as saltwater fish, seaweed, sea vegetables, shellfish, bread, cheese, and iodine-containing multivitamins.
Iodized salt is now the main source of iodine in the American diet, but only about 20 percent of the salt America eats contains the micronutrient. Increasingly popular "designer" table salts, such as sea salts and Kosher salts, usually do not have much iodine. However, the majority of salt intake in the United States comes from processed foods, and food manufacturers almost always use noniodized salt in processed foods. Add to that the ubiquitous warnings against using too much salt because of our ever-pressing issues of hypertension, congestive heart disease, and other coronary artery diseases, and iodine deficiency becomes a real threat for some people in the United States. Whereas, just a few years ago iodine was mandated by the FDA to be included in salts (and was for decades), now most medical advice states that, due to the large variety of food sources available from all over the world, iodine in salt is no longer necessary in the United States and other Western countries. Iodization of salt is now voluntary in America. It appears that iodine intake has declined by 50 percent in North America in the past 30 to 40 years and the anticipated rate of future hypothyroid cases has risen dramatically.
Before the 1920s, iodine deficiency was common in the Great Lakes, Appalachian, and Northwestern regions of the United States and Canada; however, the introduction of iodized salt has virtually eliminated the problem in those areas. Iodine deficiency can lead to goiter, hypothyroidism, and even to mental retardation in infants and children (the term "cretin" comes from the fetus not getting enough iodine while in the mother's womb).
Worldwide, the number one cause of hypothyroidism is iodine deficiency, which remains a public health problem in 47 countries, and about 2.2 billion people (38 percent of the world's population) live in areas with iodine deficiency. An article in The Lancet in 2008 stated that, "According to WHO, in 2007, nearly 2 billion individuals had insufficient iodine intake, a third being of school age. Thus iodine deficiency, as the single greatest preventable cause of mental retardation, is an important public health problem."
There are many different types and brands of iodine supplementation available over the counter. It's important, however, that you get guidance from your doctor or health professional before taking any iodine supplementation. If you take too much, you can develop hyperthyroidism.