Prenatal Phthalates Exposure and Cord Thyroid Hormones: A Birth Cohort Study in Southern Taiwan

Abstract

Background: The regulation of thyroid hormones in the early stages of gestation plays a crucial role in the outcome of a pregnancy. Furthermore, thyroid hormones are fundamental for the fetal development of all organs, including endocrine hormone changes in uterus. Endocrine disrupting chemicals have been shown to have an effect on thyroid hormone homeostasis in newborns, which affects their later development. Few studies have proposed how phthalates could alter thyroid function through several mechanisms and the possible effects on thyroid hormone homeostasis of phthalates on pregnant women. However, the effects of cord blood phthalates and prenatal phthalate exposure on thyroid hormones in newborns remain unclear. Objectives: We aim to follow up on our previous established subjects and determine the correlation between phthalate exposure and thyroid hormones in pregnant women and newborns. Materials and methods: We recruited 61 pregnant women from the Obstetrics and Gynecology Department of a medical hospital in southern Taiwan and followed up. High performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) was used to analyze urine samples for five phthalate metabolites. Serum levels of thyroid hormones were analyzed using electrochemoluminescence immunoassay (ECLIA) method. We used Spearman and Pearson correlation coefficients to evaluate the correlation between each phthalate metabolites in serum and the thyroid hormone levels in fetus and parturient. Finally, multiple logistic regression was used to explore the relationship between hormones and their corresponding phthalate metabolites in cord blood. Results: High MBP in cord blood was correlated with negative cord serum TSH in newborns (r = −0.25, p < 0.06). By using multiple linear regression after adjusting for potential confounders (gestational and maternal age), cord serum MBP levels showed a negative association with cord serum TSH (β = 0.217, p < 0.05), cord serum T4 (β = 1.71, p < 0.05) and cord serum T4 × TSH (β = 42.8, p < 0.05), respectively. Conclusion: We found that levels of cord serum TSH and T4 in newborns was significantly negatively associated with cord serum MBP levels after adjusting for significant covariate. The fall in TSH in newborns may potentially be delaying their development.

New insights on the effects of endocrine-disrupting chemicals on children

“…In newborns exposed to multiple phthalate metabolites during pregnancy, levels of cord serum TSH and FT4 were found to be significantly negatively associated with cord serum phthalate levels. 5 , 60 Effects of cord blood phthalates and prenatal exposure on thyroid hormones in newborns remain unclear, but the fall of TSH levels may potentially delay their development.…”

Indicator of thyroid hormones in newborns from mothers with diffuse-endemic goiter

“…Следовательно, отмечается постепенное (на фоне адаптации) снижение ТТГ у младенцев. Одновременно, как отмечают некоторые авторы, распространенность новорожденных с повышенным уровнем ТТГ может быть использована для определения степени дефицита йода в данном регионе [11].…”

“…Следует отметить, что диагностический критерий по определению тяжести йодной недостаточности по отношению ТТГ -у младенцев >5 мЕд/л, не был включен в версию ВОЗ 2007 г. [11], и это связывают с тем фактом, что имеется несколько обстоятельств, которые могут влиять на уровень ТТГ у младенцев (методика проведения анализов, время, используемая бумага, антисептические средства и доставка биоматериала -капиллярной крови из пятки) [3].…”

“…При этом многие ученые рекомендуют проводить мониторинг йодного статуса у беременных и в последующем у их детей путем исследования не только уровня ТТГ, но и Т3 с свободным Т4, т. к. данные более достоверно характеризуют тиреоидный статус детей, и они являются более уязвимыми к отрицательным последствиям йодного дефицита [2,11].…”

Endocrine Disrupting Chemicals’ Effects in Children: What We Know and What We Need to Learn?

“…Alterations of thyroid hormone levels in umbilical cord blood and newborns were demonstrated to be related to multiple phthalate metabolites exposure during pregnancy [ 254 , 255 ]. The effects of umbilical cord blood phthalates and prenatal phthalate exposure on thyroid hormones in newborns remain unclear, but the fall of TSH levels in newborns may potentially be delaying their development.…”