title: The Correlation between Polybrominated Diphenyl Ethers (PBDEs) and Thyroid Hormones in the General Population: A Meta-Analysis.
abstract: OBJECTIVE
  Certain epidemiological studies have suggested exposure to polybrominated diphenyl ethers (PBDEs) affect the production and secretion of thyroid hormones (TH); however, conflicting results have been reported in different studies. There is not a convincing conclusion about this debate to date.
  
  
  METHODS
  To perform a meta-analysis determining if there are correlations between PBDEs exposure and the serum levels of TH. Medical and scientific literature databases were searched for articles that met the eligibility criteria. The included articles were assessed for methodological quality. The correlation coefficient values or regression coefficient values between PBDEs and thyroid stimulating hormone (TSH) or total thyroxine (TT4) from each article were used for analysis.
  
  
  RESULTS
  Sixteen articles were included in this meta-analysis. Pearson correlation coefficients (r) were directly collected or calculated from data given in the articles. Then, Fisher's z transformation was performed to convert each correlation coefficient to an approximately normal distribution. For z values between PBDEs exposure and TSH levels, the pooled z value for 18 studies was 0.08 (95% CI: -0.06, 0.22), and indicated significant heterogeneity (I2 values = 90.7%). Subgroup analysis was performed based on the median values of serum PBDEs in each study, there was not significant heterogeneity in each of the four subgroups (I2 values <30%). In meta-analysis of z values between PBDEs exposure and the levels of TT4, the pooled z value for 11 studies was -0.02 (95% CI: -0.11, 0.08), and also indicated significant heterogeneity (I2 values = 57.6%). Similar subgroup analysis was done for the PBDEs exposures and the levels of TT4. No significant heterogeneity was shown in either of the two subgroups (I2 values = 0).
  
  
  CONCLUSIONS
  The findings in our meta-analysis indicate the effects of PBDEs on thyroid function may mainly depend on PBDEs exposure and their levels found in serum. The relationship between PBDEs exposure and changes in thyroid function seem to fit an approximate u-shaped curve. These predictions await further verification, namely a prospective longitudinal study.
authors.affiliation: Department of Endocrinology and Metabolism, Institute of Endocrinology, The First Affiliated Hospital, China Medical University, Liaoning Provincial Key Laboratory of Endocrine Diseases, Shenyang, P. R. China.
authors.forename: Xuemin
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Department of Clinical Epidemiology, Institute of Cardiovascular Disease and Center of Evidence Based Medicine, The First Affiliated Hospital, China Medical University, Shenyang, P. R. China.
authors.forename: Hailong
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Endocrinology and Metabolism, Institute of Endocrinology, The First Affiliated Hospital, China Medical University, Liaoning Provincial Key Laboratory of Endocrine Diseases, Shenyang, P. R. China.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Endocrinology and Metabolism, Institute of Endocrinology, The First Affiliated Hospital, China Medical University, Liaoning Provincial Key Laboratory of Endocrine Diseases, Shenyang, P. R. China.
authors.forename: Zhongyan
authors.initials: Z
authors.lastname: Shan
authors.affiliation: Department of Endocrinology and Metabolism, Institute of Endocrinology, The First Affiliated Hospital, China Medical University, Liaoning Provincial Key Laboratory of Endocrine Diseases, Shenyang, P. R. China.
authors.forename: Weiping
authors.initials: W
authors.lastname: Teng
authors.affiliation: Department of Endocrinology and Metabolism, Institute of Endocrinology, The First Affiliated Hospital, China Medical University, Liaoning Provincial Key Laboratory of Endocrine Diseases, Shenyang, P. R. China.
authors.forename: Xiaochun
authors.initials: X
authors.lastname: Teng
mesh_terms: D004781:Environmental Exposure / Q000009:adverse effects*; D055768:Halogenated Diphenyl Ethers / Q000009:adverse effects*; D006801:Humans; D062486:Public Health Surveillance; D013963:Thyroid Hormones / Q000097:blood*; D013974:Thyroxine / Q000097:blood
chemical_list: D055768:Halogenated Diphenyl Ethers; D013963:Thyroid Hormones; D013974:Thyroxine