BACKGROUND : Disruption of thyroid homeostasis has been indicated in human studies targeting
effects of persistent organic pollutants (POPs). Influence on the maternal thyroid system by POPs
is of special interest during pregnancy because such effects could impair infant thyroid homeostasis.
OBJECTIVES : We investigated the association between POPs and thyroid-stimulating hormone
(TSH) and thyroid hormones (THs) in mother and child pairs from the Northern Norway Motherand-
Child Contaminant Cohort Study (MISA).
METHODS : Nineteen POPs and 10 thyroid parameters were analyzed in serum from 391 pregnant
women in their second trimester. In addition, TSH concentrations in heel-prick samples from the
infants were analyzed by the Norwegian Newborn Screening program. Association studies with a
multipollutant approach were performed using multivariate analyses; partial least squares (PLS)
regression, hierarchical clustering, and principal component analysis (PCA).
RESULTS : Several POPs were significantly associated with TSH and THs: a) PFOS was positively
associated with TSH; b) PCBs, HCB, and nonachlors were inversely associated with T3, T4, and
FT4; and, c) PFDA and PFUnDA were inversely associated with T3 and FT3. After mutual adjustments
for the other contaminants, only PFDA and PFUnDA remained significantly associated with
T3 and FT3, respectively. Infants born to mothers within the highest TSH quartile had 10% higher
mean concentrations of TSH compared with children born to mothers in the lowest TSH quartile.
CONCLUSION : The present results suggest that background exposures to POPs can alter maternal
thyroid homeostasis. This research contributes to the understanding of multipollutant exposures
using multivariate statistical approaches and highlights the complexity of investigating environmental
concentrations and mixtures in regard to maternal and infant thyroid function.