Associations between urinary diphenyl phosphate and thyroid function.
Triphenyl phosphate (TPHP) is a commonly used organophosphate flame retardant and plasticizer with widespread human exposure. Data on health effects of TPHP are limited. Recent toxicological studies suggest TPHP may alter thyroid function. We used repeated measures to assess the temporal variability in urinary concentrations of the TPHP metabolite, diphenyl phosphate (DPHP), and to examine relationships between DPHP concentrations and thyroid hormones. We sampled 51 adults at months 1, 6, and 12 from 2010 to 2011. Urine samples were analyzed for DPHP. Serum samples were analyzed for free and total thyroxine (fT4, TT4), total triiodothyronine (TT3), and thyroid stimulating hormone (TSH). We assessed variability in DPHP using intraclass correlation coefficients (ICCs) and kappa statistics. We used linear mixed-effects models to examine associations between DPHP and thyroid hormones. DPHP was detected in 95% of urine samples. Mean DPHP concentrations were 43% higher in women than men. DPHP showed high within-subject variability (ICC range, 0.13-0.39; kappa range, 0.16-0.39). High versus low (≥2.65 vs. <2.65ng/mL) DPHP in all participants was associated with a 0.43μg/dL (95% confidence interval: 0.15, 0.72) increase in mean TT4levels. In sex-stratified analyses, high versus low DPHP was associated with a 0.91μg/dL (95% CI: 0.47, 1.36) increase in mean TT4in women. The association was attenuated in men (βeta=0.19; 95% CI: -0.15, 0.52). We found no significant associations between DPHP and fT4, TT3, or TSH. We found evidence that TPHP exposure may be associated with increased TT4levels, especially in women.
Department of Environmental Health, Boston University School of Public Health, Boston, MA, USA. Electronic address: ejvirgi@bu.edu.
Emma V
EV
Preston
Department of Environmental Health, Boston University School of Public Health, Boston, MA, USA.
Michael D
MD
McClean
Department of Environmental Health, Boston University School of Public Health, Boston, MA, USA.
Birgit
B
Claus Henn
Nicholas School of the Environment, Duke University, Durham, NC, USA.
Heather M
HM
Stapleton
Section of Endocrinology, Diabetes, and Nutrition, Boston University School of Medicine, Boston, MA, USA.
Lewis E
LE
Braverman
Section of Endocrinology, Diabetes, and Nutrition, Boston University School of Medicine, Boston, MA, USA.
Elizabeth N
EN
Pearce
Department of Environmental Health, Boston University School of Public Health, Boston, MA, USA.
Colleen M
CM
Makey
Department of Environmental Health, Boston University School of Public Health, Boston, MA, USA.
Thomas F
TF
Webster
D000328:Adult; D000368:Aged; D000393:Air Pollutants / Q000097:blood / Q000652:urine*; D001900:Boston; D002648:Child; D002675:Child, Preschool; D004781:Environmental Exposure; D005260:Female; D005411:Flame Retardants / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010755:Organophosphates / Q000097:blood / Q000652:urine*; D012737:Sex Factors; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D055815:Young Adult
D000393:Air Pollutants; D005411:Flame Retardants; D010755:Organophosphates; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine; C005445:triphenyl phosphate
Diphenyl phosphate; Organophosphate flame retardants; Thyroid hormones; Triphenyl phosphate