Thyroid hormone levels of pregnant inuit women and their infants exposed to environmental contaminants.
BACKGROUND
An increasing number of studies have shown that several ubiquitous environmental contaminants possess thyroid hormone-disrupting capacities. Prenatal exposure to some of them, such as polychlorinated biphenyls (PCBs), has also been associated with adverse neurodevelopmental effects in infants.


OBJECTIVE
In this study we examined the relationship between exposure to potential thyroid hormone-disrupting toxicants and thyroid hormone status in pregnant Inuit women from Nunavik and their infants within the first year of life.


METHODS
We measured thyroid hormone parameters [thyroid stimulating hormone (TSH), free thyroxine (fT(4)), total triiodothyronine (T(3)), thyroxine-binding globulin (TBG)] and concentrations of several contaminants [PCB-153, hydroxylated metabolites of PCBs (HO-PCBs), pentachlorophenol (PCP) and hexachlorobenzene (HCB)] in maternal plasma at delivery (n = 120), in umbilical cord plasma (n = 95), and in infant plasma at 7 months postpartum (n = 130).


RESULTS
In pregnant women, we found a positive association between HO-PCBs and T(3) concentrations (beta = 0.57, p = 0.02). In umbilical cord blood, PCB-153 concentrations were negatively associated with TBG levels (beta = -0.26, p = 0.01). In a subsample analysis, a negative relationship was also found between maternal PCP levels and cord fT(4) concentrations in neonates (beta = -0.59, p = 0.02). No association was observed between contaminants and thyroid hormones at 7 months of age.


CONCLUSIONS
Overall, there is little evidence that the environmental contaminants analyzed in this study affect thyroid hormone status in Inuit mothers and their infants. The possibility that PCP may decrease thyroxine levels in neonates requires further investigation.
Dallaire
Renée
R
Public Health Research Unit, Centre Hospitalier Universitaire de Québec-CHUL, Québec City, Québec, Canada.
Muckle
Gina
G
Dewailly
Eric
E
Jacobson
Sandra W
SW
Jacobson
Joseph L
JL
Sandanger
Torkjel M
TM
Sandau
Courtney D
CD
Ayotte
Pierre
P
D000328:Adult; D004781:Environmental Exposure; D004785:Environmental Pollutants; D005260:Female; D006581:Hexachlorobenzene; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D004930:Inuit; D011078:Polychlorinated Biphenyls; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000097:blood; D013963:Thyroid Hormones / Q000097:blood*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D013975:Thyroxine-Binding Proteins; D014284:Triiodothyronine / Q000097:blood; D055815:Young Adult
D004785:Environmental Pollutants; D013963:Thyroid Hormones; D013975:Thyroxine-Binding Proteins; D014284:Triiodothyronine; D006581:Hexachlorobenzene; D013972:Thyrotropin; D011078:Polychlorinated Biphenyls; D013974:Thyroxine