Female reproductive factors linked to thyroid cancer risk
Reproductive factors such as pregnancy, parity, menstruation and breastfeeding appear to be significantly associated with the risk of developing thyroid cancer, a study has found.
The study used large‐scale nationwide cross‐sectional data from 21,543 females from the Korea National Health and Nutrition Examination Survey V‐VI (2010‐2015), among whom 210 had thyroid cancer.
On logistic regression analysis, pregnancy, parity and number of reproductive years (period between menarche and menopause, excluding breastfeeding period) were significantly associated with thyroid cancer.
Specifically, the risk increased by up to sevenfold among women who had experienced pregnancy in their lifetime vs those who had never been pregnant (adjusted odds ratio [OR], 7.60; 95 percent CI, 3.02–19.13; p<0.01), by sixfold among parous vs nulliparous women (adjusted OR, 6.12; 2.93–12.71; p<0.01) and by 1.08 times among women with longer reproductive years (mean, 26.9 years; adjusted OR, 1.08; 1.06–1.11; p<0.01).
On the other hand, breastfeeding showed a protective effect against the risk of thyroid cancer (adjusted OR, 0.87; 0.80–0.96 p<0.01). Oral contraceptive use was not associated with the risk.
Findings of the present study suggests that reproductive, menstrual factors and breastfeeding can affect the development of thyroid cancer, researchers said. Additional large prospective studies are required to establish whether the relationship is causal and shed light on the definite mechanism.