[Reproductive history, contraceptives and cigarette smoke as risk factors for cancer of the thyroid in women. Case-control study].

Background: Evaluation of the influence of hormonal and reproductive factors and the role of cigarette smoking in the onset of thyroid carcinoma.

Methods: Comparison between a group of 78 female patients all living in the district of Lazio, operated for thyroid follicular or papillary carcinoma at the Third Clinical Surgery Dept., Policlinico Umberto I, Rome (Italy) from 1990 to 1997, and a group of 150 women free from neoplastic and/or hormonal pathology, recruited by the compilation of a questionnaire.

Results: Cigarette smoking can be associated with risk reduction of developing thyroid neoplasia. On the contrary, no risk variation has been associated with the number of normal pregnancies, with pregnancy interruption both spontaneous and voluntary and with anthropometric characteristics of the analysed individuals. The first pregnancy at very young age and the use of contraceptives seem to determine a risk increase of thyroid cancer, at the limit of statistical significance.

Conclusions: The antiestrogenic action of cigarette smoking exerts a protective action for thyroid carcinomas. Spontaneous or volontary interruption of pregnancy did not show a significant effect as risk factor.