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Meta-Analysis
. 2015:2015:103515.
doi: 10.1155/2015/103515. Epub 2015 Aug 3.

Reproductive Factors but Not Hormonal Factors Associated with Thyroid Cancer Risk: A Systematic Review and Meta-Analysis

Yijuan Cao  1 , Zengyan Wang  2 , Juan Gu  1 , Fangfang Hu  1 , Yujuan Qi  1 , Qianqian Yin  1 , Qingqing Sun  1 , Guotao Li  3 , Bin Quan  4
Affiliations
Meta-Analysis

Reproductive Factors but Not Hormonal Factors Associated with Thyroid Cancer Risk: A Systematic Review and Meta-Analysis

Yijuan Cao et al. Biomed Res Int. 2015.

Abstract

Many studies have investigated the association between hormonal and reproductive factors and thyroid cancer risk but provided contradictory and inconclusive findings. This review was aimed at precisely estimating this association by pooling all available epidemiological studies. 25 independent studies were retrieved after a comprehensive literature search in databases of PubMed and Embase. Overall, common hormonal factors including oral contraceptive and hormone replacement therapy did not alter the risk of thyroid cancer. Older age at menopause was associated with weakly increased risk of thyroid cancer in overall analysis (RR = 1.24, 95% CI 1.00-1.53, P = 0.049); however, longer duration of breast feeding was related to moderately reduced risk of thyroid cancer, suggested by pooled analysis in all cohort studies (RR = 0.7, 95% CI 0.51-0.95, P = 0.021). The pooled RR in hospital-based case-control studies implicated that parous women were more susceptible to thyroid cancer than nulliparous women (RR = 2.30, 95% CI 1.31-4.04, P = 0.004). The present meta-analysis suggests that older age at menopause and parity are risk factors for thyroid cancer, while longer duration of breast feeding plays a protective role against this cancer. Nevertheless, more relevant epidemiological studies are warranted to investigate roles of hormonal and reproductive factors in thyroid carcinogenesis.

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Figures

Figure 1
Figure 1
Forest plot for thyroid cancer risk related to age at menopause.
Figure 2
Figure 2
Forest plot for thyroid cancer risk related to duration of breastfeeding.
Figure 3
Figure 3
Forest plot for thyroid cancer risk related to parity.
See this image and copyright information in PMC

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