Associations between urinary phthalate monoesters and thyroid hormones in pregnant women.
BACKGROUND
Maternal hypothyroidism during pregnancy can cause adverse effects in the fetus. Scientific evidence has shown that probable thyroid-like function of some phthalates in vitro and in vivo, and phthalates exposure, can begin in utero. This study investigated the association between phthalate exposure and thyroid hormones in pregnant women.


METHODS
Serum and spot urine samples were collected from 76 Taiwanese pregnant women at second trimester. Thyroid hormones, including thyroid-stimulating hormone (TSH), triiodothyronine (T(3)), thyroxine (T(4)) and free T(4) (FT(4)) were analysed in serum samples, and five urinary phthalate monoesters, including mono butyl phthalate (MBP), monoethyl phthalate (MEP) and mono ethylhexyl phthalate (MEHP), were measured.


RESULTS
Urinary MBP, MEP and MEHP, the median levels of which were 81.8, 27.7 and 20.6 ng/ml, respectively, were the predominant substances in the urinary phthalate monoesters. Significant mild negative correlations were found between T(4) and urinary MBP (R = -0.248, P < 0.05), and between FT(4) and urinary MBP (R = -0.368, P < 0.05). After adjusting for age, BMI and gestation, urinary MBP levels showed negative associations with FT(4) and T(4) (FT(4): beta = -0.110, P < 0.001; T(4): beta=-0.112, P = 0.003).


CONCLUSIONS
Exposure to di-n-butyl phthalate (DBP) may affect thyroid activity in pregnant women, but how DBP affects thyroid function is unclear. Further studies are needed to elucidate the mechanism of action and to investigate whether any other factors related to DBP exposure alter the thyroid function.
Huang
Po-Chin
PC
Department of Environmental and Occupational Health, Medical College, National Cheng Kung Universitys, Tainan, Taiwan, Republic of China.
Kuo
Pao-Lin
PL
Guo
Yue-Liang
YL
Liao
Pao-Chi
PC
Lee
Ching-Chang
CC
D000328:Adult; D003404:Creatinine / Q000097:blood; D004051:Diethylhexyl Phthalate / Q000031:analogs & derivatives / Q000652:urine; D004781:Environmental Exposure / Q000032:analysis*; D004958:Estradiol / Q000097:blood; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D010795:Phthalic Acids / Q000652:urine*; D011247:Pregnancy; D012044:Regression Analysis; D013963:Thyroid Hormones / Q000097:blood*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D010795:Phthalic Acids; D013963:Thyroid Hormones; D014284:Triiodothyronine; C517284:monomethyl phthalate; D004958:Estradiol; D003404:Creatinine; D004051:Diethylhexyl Phthalate; C016599:mono-(2-ethylhexyl)phthalate; D013974:Thyroxine; C028577:monobutyl phthalate