BENIGN THYROID-TUMORS - GENERAL RISK-FACTORS AND THEIR EFFECTS ON RADIATION RISK-ESTIMATION

The authors examined risk factors for benign thyroid nodules and their influence on radiation effects among 544 subjects who were exposed to childhood radiation treatment for benign head and neck conditions at a Chicago, Illinois hospital during 1939-1962. In follow-up through 19 91, benign thyroid nodules were diagnosed in 131 patients. The risk of benign nodules was elevated in women (relative risk (RR) = 2.2, 95% c onfidence interval (CI) 1.6-3.2), Jews (RR = 1.7, 95% CI 1.1-2.5), col lege graduates (RR = 1.8, 95% CI 1.2-2.8), and subjects whose mother h ad cancer (RR = 1.7, 95% CI 1.2-2.5). There were increasing trends for risk with increasing body mass index in women and decreasing height i n men. Risk was increased for women who never married (RR - 3.7, 95% C I 1.6-7.3) or who never had a full-term pregnancy (RR = 2.0, 95% CI 1. 1-3.3), A significant radiation dose-response relationship was observe d that was not modified by sex, education, Jewish religion, or reprodu ctive factors. The data suggest that there are genetic, life-style (in cluding ascertainment), and hormonal factors associated with the devel opment of benign thyroid nodules.