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Thyroid hormones in relation to lead, mercury, and cadmium exposure in the National Health and Nutrition Examination Survey, 2007-2008.

Chen A, Kim SS, Chung E, Dietrich KN - Environ. Health Perspect. (2012)

Bottom Line: The geometric mean (GM) levels of blood Pb (BPb), total Hg, and Cd were 0.81 µg/dL, 0.47 µg/L, and 0.21 µg/L in adolescents and 1.43 µg/dL, 0.96 µg/L, and 0.38 µg/L in adults, respectively.The GMs of urinary Cd were 0.07 and 0.25 µg/g creatinine in adolescents and adults, respectively.In adults, blood Hg was inversely related to TT4, TT3, and FT3 and urinary Cd was positively associated with TT4, TT3, FT3, and Tg, but there were no associations with Pb.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Health, Division of Epidemiology and Biostatistics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA. aimin.chen@uc.edu

ABSTRACT

Background: Heavy metals, such as lead (Pb), mercury (Hg), and cadmium (Cd), are known toxicants, but their associations with the thyroid axis have not been well quantified at U.S. background levels.

Objectives: We investigated the relationships between thyroid hormones (total and free thyroxine [TT4 and FT4], total and free triiodothyronine [TT3 and FT3], thyroid-stimulating hormone [TSH], and thyroglobulin [Tg]) and levels of Pb, Hg, and Cd in blood and Cd in urine.

Methods: We separately analyzed a sample of 1,109 adolescents (12-19 years of age) and a sample of 4,409 adults from the U.S. National Health and Nutrition Examination Survey (NHANES) 2007-2008. We estimated associations after adjusting for age, sex, race, urinary iodine, body mass index, and serum cotinine.

Results: The geometric mean (GM) levels of blood Pb (BPb), total Hg, and Cd were 0.81 µg/dL, 0.47 µg/L, and 0.21 µg/L in adolescents and 1.43 µg/dL, 0.96 µg/L, and 0.38 µg/L in adults, respectively. The GMs of urinary Cd were 0.07 and 0.25 µg/g creatinine in adolescents and adults, respectively. No consistent pattern of metal and thyroid hormone associations was observed in adolescents. In adults, blood Hg was inversely related to TT4, TT3, and FT3 and urinary Cd was positively associated with TT4, TT3, FT3, and Tg, but there were no associations with Pb. Associations were relatively weak at an individual level, with about 1-4% change in thyroid hormones per interquartile range increase in Hg or Cd.

Conclusions: Our analysis suggests an inverse association between Hg exposure and thyroid hormones, and a positive association between Cd exposure and thyroid hormones in adults.

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Estimated thyroid hormone levels according to natural log blood total Hg or urinary Cd exposure quintiles in adults, NHANES 2007–2008. (A) TT4 by blood total Hg quintiles, (B) TT3 by blood total Hg quintiles, (C) TT4 by urinary Cd quintiles, (D) TT3 by urinary Cd quintiles.
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f1: Estimated thyroid hormone levels according to natural log blood total Hg or urinary Cd exposure quintiles in adults, NHANES 2007–2008. (A) TT4 by blood total Hg quintiles, (B) TT3 by blood total Hg quintiles, (C) TT4 by urinary Cd quintiles, (D) TT3 by urinary Cd quintiles.

Mentions: Statistically significant negative associations between blood total Hg and TT4 and FT3 were observed in adolescents (Table 2). Blood Cd was positively associated with FT3 and urinary Cd was positively associated with FT4. Table 3 shows that in adults, BPb exposure was not associated with any TH levels. Both total and organic Hg had significant negative associations with TT4, TT3, and FT3. Blood Cd was positively associated with FT4 and Tg; urinary Cd was positively associated with TT4, TT3, FT3, and Tg. In the analyses of quintiles of metal exposures and TH levels in adolescents, the dose responses were not evident [see Supplemental Material, Table S1 (http://dx.doi.org/10.1289/ehp.1205239)]. However, in adults, the dose–response patterns consistent with the modeling of continuous exposure were evident for total Hg, organic Hg, and urinary Cd (see Supplemental Material, Table S2). Figure 1 shows that total blood Hg levels were associated with lower TT4 and TT3, with the 5th quintile of exposure (≥ 2.16 µg/dL) showing the strongest associations. Urinary Cd levels were positively associated with TT4 and TT3. In contrast, no consistent patterns were found for BPb levels (see Supplemental Material, Table S2).


Thyroid hormones in relation to lead, mercury, and cadmium exposure in the National Health and Nutrition Examination Survey, 2007-2008.

Chen A, Kim SS, Chung E, Dietrich KN - Environ. Health Perspect. (2012)

Estimated thyroid hormone levels according to natural log blood total Hg or urinary Cd exposure quintiles in adults, NHANES 2007–2008. (A) TT4 by blood total Hg quintiles, (B) TT3 by blood total Hg quintiles, (C) TT4 by urinary Cd quintiles, (D) TT3 by urinary Cd quintiles.
© Copyright Policy - public-domain
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3569681&req=5

f1: Estimated thyroid hormone levels according to natural log blood total Hg or urinary Cd exposure quintiles in adults, NHANES 2007–2008. (A) TT4 by blood total Hg quintiles, (B) TT3 by blood total Hg quintiles, (C) TT4 by urinary Cd quintiles, (D) TT3 by urinary Cd quintiles.
Mentions: Statistically significant negative associations between blood total Hg and TT4 and FT3 were observed in adolescents (Table 2). Blood Cd was positively associated with FT3 and urinary Cd was positively associated with FT4. Table 3 shows that in adults, BPb exposure was not associated with any TH levels. Both total and organic Hg had significant negative associations with TT4, TT3, and FT3. Blood Cd was positively associated with FT4 and Tg; urinary Cd was positively associated with TT4, TT3, FT3, and Tg. In the analyses of quintiles of metal exposures and TH levels in adolescents, the dose responses were not evident [see Supplemental Material, Table S1 (http://dx.doi.org/10.1289/ehp.1205239)]. However, in adults, the dose–response patterns consistent with the modeling of continuous exposure were evident for total Hg, organic Hg, and urinary Cd (see Supplemental Material, Table S2). Figure 1 shows that total blood Hg levels were associated with lower TT4 and TT3, with the 5th quintile of exposure (≥ 2.16 µg/dL) showing the strongest associations. Urinary Cd levels were positively associated with TT4 and TT3. In contrast, no consistent patterns were found for BPb levels (see Supplemental Material, Table S2).

Bottom Line: The geometric mean (GM) levels of blood Pb (BPb), total Hg, and Cd were 0.81 µg/dL, 0.47 µg/L, and 0.21 µg/L in adolescents and 1.43 µg/dL, 0.96 µg/L, and 0.38 µg/L in adults, respectively.The GMs of urinary Cd were 0.07 and 0.25 µg/g creatinine in adolescents and adults, respectively.In adults, blood Hg was inversely related to TT4, TT3, and FT3 and urinary Cd was positively associated with TT4, TT3, FT3, and Tg, but there were no associations with Pb.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Health, Division of Epidemiology and Biostatistics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA. aimin.chen@uc.edu

ABSTRACT

Background: Heavy metals, such as lead (Pb), mercury (Hg), and cadmium (Cd), are known toxicants, but their associations with the thyroid axis have not been well quantified at U.S. background levels.

Objectives: We investigated the relationships between thyroid hormones (total and free thyroxine [TT4 and FT4], total and free triiodothyronine [TT3 and FT3], thyroid-stimulating hormone [TSH], and thyroglobulin [Tg]) and levels of Pb, Hg, and Cd in blood and Cd in urine.

Methods: We separately analyzed a sample of 1,109 adolescents (12-19 years of age) and a sample of 4,409 adults from the U.S. National Health and Nutrition Examination Survey (NHANES) 2007-2008. We estimated associations after adjusting for age, sex, race, urinary iodine, body mass index, and serum cotinine.

Results: The geometric mean (GM) levels of blood Pb (BPb), total Hg, and Cd were 0.81 µg/dL, 0.47 µg/L, and 0.21 µg/L in adolescents and 1.43 µg/dL, 0.96 µg/L, and 0.38 µg/L in adults, respectively. The GMs of urinary Cd were 0.07 and 0.25 µg/g creatinine in adolescents and adults, respectively. No consistent pattern of metal and thyroid hormone associations was observed in adolescents. In adults, blood Hg was inversely related to TT4, TT3, and FT3 and urinary Cd was positively associated with TT4, TT3, FT3, and Tg, but there were no associations with Pb. Associations were relatively weak at an individual level, with about 1-4% change in thyroid hormones per interquartile range increase in Hg or Cd.

Conclusions: Our analysis suggests an inverse association between Hg exposure and thyroid hormones, and a positive association between Cd exposure and thyroid hormones in adults.

Show MeSH
Related in: MedlinePlus