Association Between Malignant Tumors of the Thyroid Gland and Exposure to Environmental Protective and Risk Factors

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Abstract
Risk factors for thyroid carcinomas and adenomas were investigated using a standard questionnaire in a case-control study in Southwestern Germany, a known iodine deficiency area. A clinical registry, set up after the Chernobyl accident at the University hospital Mannheim, served as the basis for 174 incident cases of each diagnostic group. Interview data were compared within and with prevalences from a population-based matched control group of equal size from the entire area. The protective role of coffee drinking and the consumption of cruciferous vegetables, such as broccoli, were confirmed for both genders. A high consumption of tomatoes (> 200/year) was associated with an elevated risk of > 2.5 for malignant tumors but not for benign tumors in both genders. In both genders, both treatment for goiter (hyperthyroidism) and decaffeinated coffee consumption were associated with an increased risk for malignant tumors, but less so for adenomas. In women, early menarche (< 13 years) and stillbirth after first pregnancy, as well as hysterectomy, were substantial risk factors. Occupational variables and radiation, including medical indications and mammography, did not reveal particular risks. We did not address the role of regular iodine substitution, but did analyze the consumption of freshwater fish and seafood. Multivariate analyses of the most prominent risk factors confirmed the persistence of tomato consumption as a risk factor. In view of experimental evidence on the carcinogenicity of organophosphates and the neurotoxicant effect of certain agrochemicals on neuroendocrinologically regulated organs, we postulate that in Germany, importing off-season tomatoes from areas with a known history of possible inexperienced use of agrochemicals may be associated with a promoting effect for malignant neoplasias of the thyroid gland in terms of promoting already existent proliferating tissue growth.