Case-control study of female thyroid cancer--menstrual, reproductive and hormonal factors.

A case-control study including 204 histologically verified female thyroid cancer patients and an equal number of hospital controls individually matched with cases by sex, age (+/- 2 years), place of residence and time of hospitalization was performed during the period 1996-2000. In the analysis of data, univariate and multivariate conditional logistic regression, methods were applied. According to multivariate analysis, out of hormonal, menstrual and reproductive characteristics, risk factors for thyroid cancer were spontaneous abortions (odds ratio: OR = 1.89, 95% confidence interval (CI) = 1.03-3.50), oral contraceptives use (OR = 2.34, 95% CI = 1.31-4.18) and thyroid enlargement during pregnancy (OR = 16.44, 95% CI = 3.81-70.80). However, none of these three factors remained independently related to thyroid cancer after adjustment for other factors, which were significantly associated with thyroid cancer in the present study (history of residence in endemic goitre area, history of goitre or thyroid nodule, history of other endocrine diseases, radioactive iodine therapy, occupational exposure to various chemicals, family history of thyroid gland diseases and malignant tumours as well as intake of cruciferous vegetables and other vegetables, and consumption of smoked meat and cheese).