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To the Editor.—
The article by Kapdi and Wolfe warrants comment.The data presented imply that the entire group of subjects (5,505) was homogenous. This implies all exogenous drug intake was the same and that all groups were matched for age, race, environmental factors, and parity, and that the only variable was the presence of thyroid supplements. Such an assumption seems unfounded, and the implied conclusion of a relationship between thyroid supplementation and breast cancer totally unfounded.To adequately evaluate such an assumption would require a careful scrutiny of the factors cited as possible variables in addition to the evaluation of the thyroid status in both treated and untreated groups. It may be possible from such a study to determine incidence of breast carcinoma in patients who are euthyroid, who are hypothyroid, and those who are hyperthyroid. These should be grouped by age, parity, and "other" drug history such as
Hansen KB. Thyroid Supplements and Breast Cancer. JAMA. 1976;236(24):2746-2747. doi:10.1001/jama.1976.03270250013013