The Association Between Urinary Monoester Phthalates and Thyroid Hormone in Pregnant Women

Abstract

TM1-O-09 This study is aimed to investigate the association between phthalates exposure and thyroid hormones in pregnant women. Twenty-eight second-trimester pregnant women were recruited from our hospital. The single spot urine and blood samples were collected for the determination of 5 monoester phthalates by LC/MS/MS and thyroid related hormones, respectively, after signing a consent form. Information obtained from the questionnaire included demographic characteristics and phthalates exposure (cosmetic use, frequency of dietary intake, and consumer plastic products usage). Median levels of 5 urinary phthalate metabolites, including monomethyl phthalate (MMP), monoethyl phthalate (MEP), monobutyl phthalate (MBuP), monobenzyl phthalate (MBzP), mono-2-ethylhexyl phthalate (MEHP), were as follows: MBuP (92.3 ppb), MEP (31.6 ppb), MEHP (24 ppb), MMP (5.4 ppb), and MBzP (0.9 ppb). MBuP (100%), MEHP (100%) and MEP (96.5%) were detected from most of the samples, but MMP and MBzP were identified only in 46.4% and 21.4% samples, respectively. No associations were found between the levels of 5 urinary monoester phthalates and demographic characteristics (age, BMI, and others). The MBuP and MEHP levels in urine samples from pregnant women in Taiwan were 6 and 20 times higher than those in Americans. Significant negative correlation between the levels of MBuP and T3 and Free T4 (T3: R2 = 0.177, P = 0.033; FT4: R2 = 0.231, P = 0.013) were found, respectively, indicated the probable anti-thyroid effect in pregnant women during the second trimester. After correction of urinary creatinine, the median levels were as follows: MBuP-c (346.4 μg/g creatinine), MEP-c (123.1 μg/g creatinine), MEHP-c (86.2 μg/g creatinine), MMP-c (13.1 μg/g creatinine), and MBzP-c (3.1 μg/g creatinine). Significant correlation between the level of urinary MBuP-c and MEHP-c in pregnant women were found and showed that the exposure sources of DBP may be similar to DEHP (R2 = 0.687, P < 0.01). All samples were separated into high- and low-level groups by median levels of adjusted-urinary monoester phthalates. The consumption of ruminants in high MEHP level group and the use of personal care products in high MEP level group were significant higher than the low-level group, respectively. Estimated daily intake dose (DIest) of 5 phthalates in pregnant women were calculated from the level of urinary monoester phthalates based on the pharmacokinetics model of PAEs. The calculated median DIest of 5 phthalates in pregnant women were 9.28 μg/kg per day (DBP), 5.17 μg/kg per day (DEHP), 3.01 μg/kg per day (DEP), 0.3 μg/kg per day (DMP) and <0.1 μg/kg per day (BBP). The calculated median DIest of DBP and DEHP of pregnant women in Taiwan were 5 and 7 times higher than those in Americans.