Associations between brominated flame retardants in human milk and thyroid-stimulating hormone (TSH) in neonates

Abstract

Background Brominated flame retardants (BFRs) have been in widespread use in a vast array of consumer products since the 1970s. The metabolites of some BFRs show a structural similarity to thyroid hormones and experimental animal studies have confirmed that they may interfere with thyroid hormone homeostasis. A major concern has been whether intrauterine exposure to BFRs may disturb thyroid homeostasis since the fetal brain is particularly susceptible to alterations in thyroid hormones. However, few reports on newborns have been published to date. Objectives To evaluate the association between BFRs and neonatal thyroid-stimulating hormone (TSH). Methods We studied six polybrominated diphenyl ethers (PBDEs) measured in milk samples from 239 women who were part of the “Norwegian Human Milk Study” (HUMIS), 2003–2006. Hexabromocyclododecane (HBCD) and BDE-209 were measured in a subset of the women (193 and 46 milk samples, respectively). The milk was sampled at a median of 33 days after delivery. TSH was measured in babies three days after delivery as part of the routine national screening program for early detection of congenital hypothyroidism. Additional information was obtained through the Medical Birth Registry and questionnaires to the mothers. Results The PBDE concentrations in human milk in Norway were comparable to concentrations reported from other European countries and Asia, but not the US and Canada where levels are approximately one order of magnitude higher. We observed no statistically significant associations between BDE-47, 99, 153, 154, 209 and HBCD in human milk and TSH in models adjusted for possible confounders and other environmental toxicants including polychlorinated biphenyls (PCBs). Conclusions We did not observe an association between TSH and exposure to HBCD and PBDEs within the exposure levels observed.

Scientific Opinion on Hexabromocyclododecanes (HBCDDs) in Food

“…One caveat, however, could be the limited number of samples, which hampered evaluation of weak or moderate associations. Eggesbø et al (2011) studied the association between levels of HBCDDs in human milk and neonatal thyroid-stimulating hormone (TSH). No association was found adjusting for a number of confounders, including environmental toxicants.…”

“…To evaluate the association between HBCDDs and neonatal TSH, Eggesbø et al (2011) studied HBCDDs measured in milk samples from 193 women who were part of the 'Norwegian Human Milk Study' (HUMIS), [2003][2004][2005][2006]. TSH was measured in babies three days after delivery as part of the routine national screening program for early detection of congenital hypothyroidism.…”

Impact of Brominated POPs on the Neurodevelopment and Thyroid Hormones of Young Children in an Indoor Environment—A Review

“…Many epidemiological studies that evaluate associations of PBDEs exposure and thyroid hormones in adults and newborns have been published previously, but their results are not consistent (Hagmar et al, 2001;Mazdai et al, 2003;Herbstman et al, 2008;Turyk et al, 2008;Dallaire et al, 2009;Kim et al, 2009;Roze et al, 2009;Chevrier et al, 2010;Zhang et al, 2010;Chevrier et al, 2011;Eggesbø et al, 2011;Gascon et al, 2011;Lin et al, 2011). A few studies report the negative impact of cord blood PBDEs on levels of human thyroid hormones after in utero exposure (Herbstman et al, 2008;Lin et al, 2011), but most studies conducted in humans have found no correlations.…”

“…Breast milk HBCD levels are positively correlated with the number of stereo and video electronics in a home, and are lower in women who regularly choose organic foods compared to those who do not, according to as series of tests performed on Boston mothers (Carignan et al, 2012). Eggesbø et al (2011) argues that breast milk HBCDs are not related to cord blood TSH. Asante et al (2011) calculates that the ΣHBCDs daily intake for a breastfed infant through breastfeeding is 0.003 µg/kg b.w./day in Ghana.…”

“…Log FT4 and log IGF-1 has negative significant associations with higher log BDE-99 and log BDE-85 levels, respectively (Shy et al, 2012). A Norwegian Human milk Study (HUMIS) finds no significant association between BDE-47, 99, 153, 154, and 209 in breast milk and TSH in neonates (Eggesbø et al, 2011). In contrast, a higher serum PBDE level is correlated with lower serum TSH values in epidemiological studies in adult men and women, including 270 pregnant American women around their 27th week of gestation , and 308 male Great Lakes sport fish consumers (Turyk et al, 2009), and 110 males consuming Baltic Sea fish (Hagmar et al, 2001).…”