IN 1976, Kapdi and Wolfe1 reported that among women undergoing mammography, the prevalence of breast cancer was higher among those who had received thyroid hormone therapy than among those who did not. A reanalysis of the published data2 showed that breast cancer frequency correlated with increasing age, and that within each group there was no clear-cut relationship with the presence or duration of thyroid hormone therapy. In a companion article, the American Thyroid Association3 reviewed the biological and statistical evidence for a role of thyroid hormone therapy in the cause and pathogenesis of breast cancer. They found the evidence for this relationship tenuous, and recommended that patients taking thyroid hormones for well-established indications continue to take their medications.
In a case-control study testing menstrual and reproductive hypotheses relating to breast cancer risk at the University of Iowa, we have collected information concerning the use and duration of
Wallace RB, Sherman BM, Bean JA, Leeper J. Thyroid Hormone Use in Patients With Breast CancerAbsence of an Association. JAMA. 1978;239(10):958. doi:10.1001/jama.1978.03280370054025
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