Date of Award

1-1-2019

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Yawei Zhang

Abstract

Abstract

Background: Thyroid hormones are fundamental in regulating normal body functions like metabolism, development, and reproduction. There are a limited number of studies examining the association between thyroid dysfunctions and heavy metals, particularly population-based studies. The current study aimed to examine this relationship in the U.S. population.

Method: The current study used data of the National Health and Nutrition Examination Survey from 2007 to 2012. Study population included adults older than 20 years old without any medication that might impact thyroid hormones. Based on the clinical standard of thyroid dysfunctions, eligible participants were classified into two groups by their thyroid hormones: abnormal (either subclinical or overt thyroid disease) and normal. Both blood and urinary heavy metals were categorized into quintiles. Multivariate logistic regressions were performed to explore the effect of heavy metals in thyroid dysfunctions.

Results: Among 4207 study participants, 302 (7.2%) of them had abnormal thyroid function, including 274 (90.7%) subclinical diseases (164 hypothyroidism and 110 hyperthyroidism) and 28 (9.3%) overt diseases (22 hypothyroidism and 6 hyperthyroidism). Moreover, the current study found that urinary cadmium (OR: 2.05, 95% CI: 1.03, 4.06), antimony (OR: 2.24, 95% CI: 1.27, 3.94), and tungsten (OR: 2.38, 95% CI: 1.02, 5.54) were significantly associated with increased odds of thyroid dysfunctions.

Conclusion: Environmental exposure to heavy metals may pose particular risk to thyroid problems. The limited number of overt diseases prevented us from analyzing the effect of heavy metal exposure in relation to different thyroid disease status. Future studies should be warranted to fully understand the association between heavy metal and specific thyroid dysfunction.

Comments

This is an Open Access Thesis.

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