Reproductive Risk Factors for Thyroid Cancer: A Prospective Cohort Study in Khon Kaen, Thailand

Background: Because of the gender disparity in the incidence of thyroid cancer, this study aimed to determinethe association between reproductive factors and thyroid cancer.
Methods: A total of 10,767 eligible women fromthe Khon Kaen Cohort, recruited and interviewed between 1990 and 2001, were followed up until 2011. Thedata were linked to the Khon Kaen Population-Based Cancer Registry to detect thyroid cancer cases.
Results:There was 17 thyroid cancer cases detected, an incidence of 11.2 per 100,000 person-years, of which 70.6 % werepapillary tumors. The incidence was apparently greater among those with an early age of menarche, nulligravidawomen, and oral contraceptive users. Conlusions: There was a trend for thyroid cancer to develop in relationto longer estrogen exposure. This evidence is inconclusive but warrants further investigation.