Reproductive factors and thyroid cancer risk: Meta‐analysis

Abstract Background Assessed pooled risk on reproductive factors and oral contraceptives (OC) on thyroid cancer (TC) using published studies (1996‐2017). Methods Summary odds ratio (OR) for case‐control studies (n = 10) and risk ratio (RR) for cohort studies (n = 9) was done. Results OR was 1.43 (95% CI: 1.16‐1.77) for age at menarche >14 years, 1.49 (95% CI: 1.19‐1.86) for parity >2, 1.38 (95% CI: 1.18‐1.61) for miscarriage/abortion, and 2.05 (95% CI: 1.39‐3.01) for artificial menopause. A protective effect (ORs: 0.85; 95% CI: 0.72‐0.99) on TC was observed for prolonged use of OCs. RR was 1.17 (95% CI: 0.90‐1.57) for age at menarche >14 years, 1.10 (95% CI: 0.94‐1.27) for parity >2, 1.20 (95% CI: 1.03‐1.40) for miscarriage/abortion, and 2.16 (95% CI: 1.41‐3.31) for artificial menopause and protective effect (RR: 0.78; 95% CI: 0.65‐0.92) for prolonged use of OCs. Conclusions This meta‐analysis supports an association due to changes in female hormones during menstrual cycle and pregnancy with the risk of TC and explains female preponderance.