Oprah's Thyroid

My wife Romi, a big Oprah fan, showed me the October 2007 issue of O Magazine, in which she discussed her recent struggle with hypothyroidism (low thyroid function). Oprah's public discussion of her health issues has brought widespread attention to this condition. Thyroid hormone is sometimes called the "master hormone" since it affects every system in the body. That's why I wanted to spend some time educating my readers about this essential element to good health.

The thyroid gland is a butterfly-shaped gland at the base of the neck. It produces the thyroid hormones levothyroxin (T4) and triiodo-thyronine (T3). About 80% of thyroid hormone is T4 and about 20% is T3. T4 is inactive and is converted into active T3 in different tissues in the body.

This is why low thyroid function can cause such wide-ranging symptoms. According to the Merck Manual, the American Association of Clinical Endocrinologists, and the Thyroid Foundation of America symptoms of hypothyroidism in adults include feeling cold; depression; fatigue; weight gain; inability to lose weight; coarse, dry hair that is brittle and falling out; constipation; dry, coarse skin; puffiness or swelling around the eyes; joint aches; restlessness; forgetfulness; decreased sex drive; and more frequent infections. And this is just a partial list. Low thyroid function can also occur in neonates and children, which requires immediate medical attention as it can cause stunted growth and developmental delays.

Within adults there are two general categories of hypothyroidism--autoimmune and non-autoimmune. An autoimmune condition is one where the immune system attacks the person's own tissues. Autoimmune thyroid dysfunction is called Hashimotos Thyroiditis after the doctor who discovered it in 1912. There appears to be a genetic link, as Hashimoto Thyroiditis tends to run in families. Therefore, if a relative of yours has been diagnosed with an autoimmune thyroid condition and you are experiencing any of the symptoms above, you may want to get your thyroid tested. More on thyroid testing in a moment.

If the reason for low thyroid function is not an autoimmune condition, there are several explanations. First, some medications and diseases may decrease thyroid function. Second, it may be that the conversion of T4 (inactive thyroid hormone) to T3 (active thyroid hormone) is not happening well enough. This conversion requires the minerals selenium and zinc. If a person is deficient in either of these nutrients, they could have difficulty creating T3. This condition is called "functional hypothyroidism" because your thyroid gland is producing enough of the thyroid hormones, but they're not being transformed into the active form. Additionally, high levels of cortisol, a stress hormone secreted when people are under stress, inhibits the creation of T3.

Finally, thyroid hormones come from the phenylalanine, an essential amino acid, meaning that your body cannot produce it, but that it must be ingested from food or dietary supplements. Phenylalanine is transformed in the body to tyrosine, which requires iron, and then down its pathway to form thyroid hormones.

While there can be many different explanations for the myriad symptoms associated with hypothyroidism, a comprehensive thyroid evaluation includes a physical exam and blood tests for TSH (thyroid stimulating hormone), Free T4, Total T3, red blood cell intracellular selenium and zinc, serum ferritin (the most sensitive laboratory indicator of iron deficiency) and plasma amino acids. If an autoimmune hypothyroid condition needs to be ruled out, then your doctor will order an antithyroglobulin antibody and antithyroid microsomal antibody blood tests.

Unfortunately, conventional medical screening for thyroid function does not test for the actual thyroid hormones themselves or for any of the nutritional factors required to produce and activate thyroid hormones. Instead, the standard screening test for low thyroid function is a measurement of TSH, which is actually produced in a region of the brain called the anterior pituitary gland. Its role is to stimulate the production T4 and T3 in the thyroid gland. In "functional hypothyroidism" the TSH and T4 are normal, but the T3 is low. This may simply be due to low selenium or zinc.

People who only receive the conventional medical workup can experience depression, fatigue, difficulty losing weight, and frequent coldness when the underlying cause may be low thyroid function because of nutritional deficiencies and/or chronic stress. I have had many cases of people with normal TSH, normal T4 and low T3, which have been corrected by identifying nutritional deficiencies and prescribing those nutrients to the patients.

This leads me to the interpretation of the TSH test. Many labs are still relying on the old reference range, which has an upper limit of normal of 5.0. An elevated TSH is the laboratory criteria for diagnosing hypothyroidism. However, what is considered "normal" has been changing. In 2002 the American Association of Clinical Endocrinologists (AACE) recommended that upper limit of normal be lowered to 3.0, and also in 2002 the National Academy of Clinical Biochemistry (NACB) suggested the correct upper range of normal will someday be lowered to 2.5.

Many clinicians use a combination of laboratory values and symptoms to determine when to treat, and most, including myself, will consider prescribing thyroid replacement hormone when the TSH is 2.5-5.0 when the patient is symptomatic and other causes are ruled out. If your TSH is greater than 2.5 and you are symptomatic, you may want to discuss with your doctor if it's appropriate to try low-dose thyroid replacement hormone.

The thyroid gland is incredibly important. If you have not been getting regular thyroid tests at your annual physicals, I recommend you do so. At the very least, get your TSH checked regularly.

(Note: Dr. Neustadt was voted as one of the leading thyroid doctors in the Thyroid Top Doctors Directory.)