Thyroid Function and Cancer Risk: A Prospective Population Study

Background: It has been hypothesized that thyroid function may influence cancer risk, but few studies with adequate statistical power have investigated this question, and the results have not been consistent. Methods: In a prospective study of 29,691 people (19,710 women and 9,981 men) without previously known thyroid disease, thyrotropin was measured at baseline, and cancer incidence was recorded during 9 years of follow-up. Using Cox regression analysis, we studied the associations (hazard ratios) of thyrotropin categories with total cancer risk, and specifically, with risk of lung, colon, prostate, and breast cancer adjusted for age, sex, and smoking status. Results: Low thyrotropin levels (