Dr. Theodore C. Friedman, M.D., Ph.D. is Associate Professor of Medicine-UCLA, Endocrinology Division, and is also an endocrinologist in private practice. For more information about his practice, see www.goodhormonehealth.com.
In this article, he shares his thoughts about hypothyroidism diagnosis and treatment.
Hypothyroidism is a relatively common disorder. It affects more women then men, but I happen to be one of the men who does have it. Symptoms of hypothyroidism include fatigue, gradual weight gain, constipation, muscle aches, joint pain, feeling cold, menstrual irregularities, weakness, hair loss, dry, cold skin and slow reaction time. Many patients will have a goiter (enlarged thyroid). Although it has received much discussion, I believe low body temperature is not a reliable sign of hypothyroidism.
The incidence of hypothyroidism increases with increasing age. In other words, the older we get, the more likely a thyroid deficiency will show up. The most common cause of primary hypothyroidism (hypothyroidism originating in the thyroid gland itself), is Hashimotos Thyroiditis. Hashimoto's is an autoimmune condition. The body's own antibodies attack the thyroid gland and destroy it, leading to hypothyroidism. Hashimotos Thyroiditis may be a manifestation of multiple autoimmune syndromes and may occur in families. Hypothyroidism can also be due to a pituitary problem (central hypothyroidism).
Diagnosing all types of hypothyroidism is important, because treatment with thyroid hormone will improve symptoms in patients with hypothyroidism, but is unlikely to help those who do not have hypothyroidism. In primary hypothyroidism, the thyroid gland, located in the neck, is less able to produce the thyroid hormones, T4 and T3. The pituitary gland, located in the head, responds to this deficiency by secreting more TSH. Thus, in more mild cases of primary hypothyroidism, T4 and T3 levels are normal, but the TSH is high. In more severe cases, T4 and T3 levels drop. Although the normal range for TSH is often between 0.5 and 5 mU/mL, values at the high end of the normal range may be abnormal. T3 is the more bioactive hormone compared to T4, but T4 is more stable in the circulation.
My approach to diagnosing hypothyroidism is to start with a careful history and physical. Then an Endocrinologist should perform a hands-on thyroid examination to determine if the patient has a goiter. Blood TSH, free T4, free T3 and anti-TPO antibodies should be tested. Patients with an enlarged thyroid and/or a positive anti-TPO antibody test AND a TSH greater than 4.0 mU/mL should be considered to have primary hypothyroidism. Patients without an enlarged thyroid and without a positive anti-TPO antibody test but WITH a TSH greater than 7.5 mU/mL should also be considered to have primary hypothyroidism. Patients with a free T4 of less than 0.9 mg/dL and a TSH less than 1.0 mU/mL are likely to have central hypothyroidism. Patients with symptoms of hypothyroidism but who do not meet these criteria should be watched and retested in 6 months.
Once hypothyroidism is diagnosed, there are many treatment options, including synthetic L-thyroxine (T4) preparations (Synthroid, Levoxyl and Unithroid), synthetic L-triiodothyronine (T3) preparations (Cytomel), synthetic T4/T3 combinations (Thyrolar) and dessicated thyroid preparations (Armour, Naturethroid, Bio-Throid, and Westhroid). All of the L-thyroxine preparations contain the same active ingredient, but contain different fillers and have different quality control. Until recently, Synthroid did not have FDA approval, but now all L-thyroxine preparations have FDA approval. Thyrolar and the dessicated thyroid preparations probably have a higher T3/T4 ratio than desirable and thus, I often give a lower amounts of these preparations supplemented with T4.
Most endocrinologists use L-thyroxine preparations for the initial treatment of all forms of hypothyroidism. Although the use of L-thyroxine (T4) compared to L-triiodothyronine (T3) may be surprising as T3 is the more bioactive thyroid hormone, T4 is most frequently used. This is because tissues convert T4 to T3 to maintain physiologic levels of the T3. Thus, administration of T4 results in bioavailable T3 and T4. As T4 is more stable than T3, T4 therapy gives even blood levels, while T3 therapy leads to high levels after taking the medicine and low levels before the next dose. Armour thyroid is the least expensive preparation. Because Armour thyroid comes form pig thyroids, some Endocrinologists feel that there is high pill to pill variability, but this is unlikely to be true.