Case-control study on association of female reproductive factors with risk of papillary thyroid cancer

Background  Papillary thyroid cancer is the result of a variety of pathogenic factors. The prevalence of papillary thyroid cancer varies greatly in different regions, and the disease is more harmful to women.

Objective  This study aims to explore the relationship between reproductive factors and papillary thyroid cancer, and to provide basic data for prevention and control of the disease.

Methods  A 1∶1 age (±3 years) matched case-control study was conducted in 331 pairs of newly confirmed papillary thyroid cancer cases and controls from two hospitals in Shanghai from November 2012 to December 2013. Comparisons were made in the history of menstruation, pregnancy, gynecological and breast diseases, and other variables between the two groups.

Results  The results of univariate analysis indicated that the proportions of education below bachelor degree, married, and mainly manual workers in the case group were significantly higher than those in the control group (P<0.05); the proportion of those with a family history of thyroid diseases in the case group was significantly higher than that in the control group (P<0.05); the proportions of the cases with irregular menstruation (77.34%), a history of using oral contraceptive or hormone drugs (24.77%), a history of benign gynecological diseases (31.72%), and a history of gynecological surgery (9.67%) were significantly higher than the proportions in the control group (P<0.05). After adjusting potential confounding factors such as history of CT examination, age, kinds of family salt, total iodine intake every day, education level, occupation, marital status, body mass index, and family history of thyroid diseases, the results of multiple logistic regression analysis showed that irregular menstruation (OR=1.767, 95%CI: 1.122-2.782; P=0.014), surgical menopause (OR=12.787, 95%CI: 3.202-51.057; P<0.001), pregnancy >1 time (OR =2.490, 95%CI: 1.196-5.184; P=0.015), and the history of using oral contraceptive or hormone drugs (OR=2.389, 95%CI: 1.338-4.268; P=0.003) were the risk factors of papillary thyroid cancer.

Conclusion  Irregular menstruation, surgical menopause, history of pregnancy, and history of using oral contraceptive or hormone drugs might be the risk factors of papillary thyroid cancer. To reduce the incidence of papillary thyroid cancer, strengthened health education and rational use of contraceptives are recommended.