Date of Award

January 2013

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Adrienne S. Ettinger

Abstract

Thyroid hormones play a crucial role in the functions of the nervous, reproductive, and cardiovascular systems in humans and have been shown to be sensitive to potential disruption of normal function by environmental contaminants. Several mechanisms have been studied in the role of environmental chemical exposure in alteration of thyroid hormones, including interference in iodine transport, thyroid hormone-binding proteins, deiodinases, and receptor binding. Uranium is a naturally occurring heavy metal that is found in the form of minerals in rocks, soil, surface water, groundwater, air, plants, and animals. The general population is primarily exposed to uranium through ingestion of uranium-contaminated food or water. We sought to examine the potential association between urinary uranium levels and serum thyroid hormones and antibodies in the U.S. population, using data from the National Health and Nutrition Examination Survey (2007-2010).

We used multiple linear regression and multiple logistic regression models to investigate the potential association between environmental uranium exposure and thyroid function. Environmental uranium exposure was measured by urinary uranium concentration. Thyroid function was measured by serum concentrations of thyroid stimulating hormone (TSH), total and free thyroxine (TT4 and FT4, respectively), total and free triiodothyronine (TT3 and FT3), thyroglobulin (Tg), thyroglobulin antibody (TgAb), and thyroperoxidase antibody (TPOAb). We observed a negative linear relationship between urinary uranium and serum TT4 levels and a positive linear relationship between urinary uranium and serum thyroglobulin antibodies. Furthermore, subjects with elevated serum TSH had higher odds and those with elevated serum TT3 had lower odds of having been exposed to environmental uranium compared to those with lower serum TSH and TT3, respectively. More research is needed to identify specific mechanisms by which uranium affects thyroid function and to examine the association in populations with higher-than-normal exposures to uranium.

Comments

This is an Open Access Thesis.

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