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December 13, 1976

Thyroid Supplements and Breast Cancer

Author Affiliations

Tufts University School of Medicine New England Medical Center Boston

JAMA. 1976;236(24):2746. doi:10.1001/jama.1976.03270250013011

To the Editor.—  The article by Kapdi and Wolfe relating thyroid hormone supplements to breast cancer requires comment. (1) It is important to distinguish between those patients receiving dessicated thyroid or levothyroxine to see if the statistical association is true for both. Since estrogens have been used to fatten cattle, it is possible, albeit unlikely, that enough estrogen could be given with dessicated thyroid over many years to result in an increased risk of breast cancer.1 (2) The indications for thyroid hormone use are not spelled out and, in fact, are misleading in the article. Although the title specifically states that the supplements were given for hypothyroidism, the methods section states that thyroid hormones were also given for simple goiter. Is there a difference in the results for these two groups? How many patients had thyroid nodules? (3) The criteria for diagnosing hypothyroidism initially are not given. As an