[Biological risk factors for differentiated thyroid cancer]

Apart from the two relatively well documented risk factors for thyroid cancer i.e. iodine deficiency and ionising radiation, the mechanism of carcinogenesis involves a number of biological and environmental factors. The aim of the study was to analyse the selected biological and environmental risk factors in patients with differentiated thyroid cancer in comparison with a reference group in a case-control study.

Both the group of 188 women and 30 men with thyroid cancer including 92 with follicular carcinoma and 126 with papillary carcinoma and the control group of 287 women and 58 men were subjected to the examination. All the study participants were given a standard questionnaire and underwent physical examination including thyroid USG, blood hormone levels and urine iodine concentration. The following risk factors were included in the analysis: family history, sex, age, thyroid morbidity, employment, body weight, hormone replacement therapy in women, cigarette smoking. In both groups with thyroid cancer women predominant with the female to male ratio 6.7 in follicular carcinoma and 6.0 in the papillary variant. In both groups of diagnoses the mean age was high--above 50, higher in men than in women. Over 70% of the patients with thyroid cancer had nodular goitre before the detection of cancer. In the control group the proportion of diagnosed goitre was slightly above 10%. A significantly more frequent hormone replacement therapy and contraception and more frequent miscarriages in women with thyroid cancer were noteworthy. One may assume that initiation, promotion and progression of the neoplastic process in the thyroid is triggered by a number of factors, both biological and environmental, and only multifactorial analysis may provide an insight into the mechanisms of carcinogenesis followed by initiation of preventives measures in appropriate cases.