Reproductive and menstrual factors and risk of differentiated thyroid carcinoma: The EPIC study

Abstract

Differentiated thyroid carcinoma (TC) is threefold more common in women than in men and, therefore, a role of female hormones in the etiology of differentiated TC has been suggested. We assessed these hypotheses in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Among 345,157 women (mean age 51) followed for an average of 11 years, 508 differentiated TC cases were identified. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards regression models. No significant associations were observed between differentiated TC risk and number of pregnancies, breast feeding, menopausal status, and age at menarche and at menopause. Significant associations were found with history of infertility problems (HR 1.70; 95% CI 1.12–2.60), a recent pregnancy (HR for ≤5 vs. >5 years before recruitment 3.87; 95% CI 1.43–10.46), menopause type (HR for surgical vs. natural menopause: 2.16; 95% CI 1.41–3.31), oral contraceptive (OC) use at recruitment (HR: 0.48; 95% CI 0.25–0.92) and duration of OC use (HR for ≥9 vs. ≤1 year: 0.66; 95% CI: 0.50–0.89). An increased risk was also found with hormone replacement therapy use at recruitment (HR = 1.30, 95% CI 1.02–1.67), but this was not significant after adjustment for type of menopause (HR = 1.22, 95% CI 0.95–1.57). Overall, our findings do not support a strong role of reproductive and menstrual factors, and female hormone use in the etiology of differentiated TC. The few observed associations may be real or accounted for by increased surveillance in women who had infertility problems, recent pregnancies or underwent surgical menopause.

Menstrual and reproductive history and use of exogenous sex hormones and risk of thyroid cancer among women: a meta-analysis of prospective studies

“…The borderline significant 20 % reduction (I 2 = 0 %) in thyroid cancer risk for women that were post-menopausal (compared to perior premenopausal) at enrolment disappeared after dropping the paper by Zamora-Ros et al [30], from which we could only use an unadjusted estimate.…”

Breastfeeding and thyroid cancer risk in women: A dose-response meta-analysis of epidemiological studies

“…Besides, the highest category vs. the lowest category of duration of breastfeeding was suggested to be significantly associated with thyroid cancer risk in several cohort studies and case-control studies [10, 11]. On the other hand, some other epidemiological studies did not suggest a clear relationship between breastfeeding and thyroid cancer risk [12–19]. Considering that for each individual study the detected effect size may be limited by the relevant sample size, a summary of available evidence will be needed to clarify whether breastfeeding is significantly associated with thyroid cancer risk.…”

Prospective study of seaweed consumption and thyroid cancer incidence in women

“…After age (continuous)-adjusted HRs and 95% CIs were calculated (Model 1), we further adjusted the models with baseline smoking and drinking status (current, past, never), BMI (kg/m 2 ) (< 18.5, 18.5-25, ≥ 25), education level (attended school up to 18 years old, yes or no), family history of any kind of cancer (yes or no), fish consumption ('less than 1-2 times/week', '3-4 times/ week', 'almost daily'), menopausal status (yes or no), female sex-hormone used (ever, never), gynecological cancer screening (yes or no), gravid, and parity ('never', '1', '2', '3', ' ≥ 4') (Model 2). These variables were selected as covariates because they were known or suspected to confound the association (Cady et al, 1979;Sokic et al, 1994;Bosetti et al, 2001;Mack et al, 2002Mack et al, , 2003Pham et al, 2009;Santin and Furlanetto, 2011;Schonfeld et al, 2011;Kabat et al, 2012aKabat et al, , 2012bMarcello et al, 2012;Przybylik-Mazurek et al, 2012;Cash et al, 2013;Dong et al, 2013;Jung et al, 2013;Schmid et al, 2013;Brown et al, 2014;Zamora-Ros et al, 2014). Initially, we included history of blood transfusion and/or liver diseases in the final model because they were associated with a higher incidence of thyroid cancer in this population (Fujino et al, 2004).…”