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Am Fam Physician. 2002;65(11):2212-2214

to the editor: I read with interest your article, “Treatment of Hypothyroidism.”1 I found the article informative, but I do have one disagreement. Dr. Hueston’s discussion of “subclinical hypothyroidism” suggests that patients with thyroid-stimulating hormone (TSH) levels between 6 and 10 may not progress to overt hypothyroidism and do not necessarily need to be treated. The author recommends an “individualized” approach and gives several parameters to aid in decision-making. One important factor is missing from this discussion: the lipid panel. Patients with “mild thyroid failure” (the new term for subclinical hypothyroidism, since many of these patients have a real clinical problem) usually have dyslipidemia, which may be improved with thyroid hormone replacement. Indeed, mild hypothyroidism is a risk factor for atherosclerosis.

I had the benefit of serving on two expert panels on this illness (funded by the makers of Synthroid). However, lead investigators have convinced me that all patients with an elevated TSH level should be treated unless a contraindication is present. Improvement in several health parameters are often observed in patients who receive treatment, including improved well-being (patients who did not realize they were tired until they felt better), improved lipid panel, and modest weight loss. These patients are often overweight and lose weight much easier when their TSH is normal.

In summary, I consider patients with an elevated TSH level as having hypothyroidism, and patients with normal free thyroxine (T4) level as having mild thyroid failure, which is a real condition. Why should physicians wait to treat these patients until they, if ever, progress to worse disease? Early treatment is beneficial, especially considering the lipid profile that results from an elevated TSH level.

Letters to the Editor

in reply: I appreciate Dr. Scherger’s comments regarding my article1 on hypothyroidism in AFP. The issue of small elevations of thyroid-stimulating hormone (TSH) with normal thyroxine (T4) levels is still controversial. While it is recognized that hypothyroidism is clearly associated with elevations in cholesterol (and hypercholesterolemia),2 there are no population-based data showing that persons with subclinical hypothyroidism are more likely to have higher cholesterol levels. Treatment studies of thyroid in this population have had only a small number of participants,35 included patients with elevated TSH levels after thyroid ablation therapy,4 and have not compared the effects of thyroid replacement therapy with other treatment modalities for hyperlipidemia, such as statins. So, I do not believe it is clear that the best course of treatment for these patients is thyroid replacement.

However, given these limitations, a patient at high risk for cardiac disease (e.g., a woman who has had a previous cardiovascular event, has diabetes, is a smoker, or has a strong family history of atherosclerosis) treatment for subclinical hypothyroidism with low doses of thyroxine probably carries more benefits than risks. For elderly, white women (which is the typical demographics of this population) with low risk of cardiac disease, the risk of osteopenia from excessive thyroid use may outweigh any benefits of thyroid replacement. Therefore, I think we must individualize care for our patients with this condition rather than advocating blanket therapy with thyroxine.

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This series is coordinated by Kenny Lin, MD, MPH, deputy editor.

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