Thyroid Supplements and Breast Cancer

To the Editor.—  We were alarmed to read (and to have seen reported in the news media) the article concerning the possible relationship between thyroid medication and breast cancer. Many thousands of women are taking thyroid supplements and may be frightened by these announcements. We have, in fact, received several anxious phone calls since the article appeared.Certain objections to the communication are sufficiently strong to cast doubt on the conclusions of this article and to suggest that the problem be reviewed.

1. The patient population referred to the Hutzel Hospital screening clinic is not defined. There are no data concerning socioeconomic levels and so forth. The startlingly high incidence of breast cancer in these patients does indeed indicate a very strong preselection for cancer. The "control population" (those not taking supplements) had an incidence of breast cancer greater than 6%. A breast cancer patient is defined as somebody who