Baccarelli, AndreaGiacomini, Sara MCorbetta, CarloLandi, Maria TeresaBonzini, MatteoConsonni, DarioGrillo, PaoloPatterson, Donald GPesatori, Angela CBertazzi, Pier Alberto2010-11-162008Baccarelli, Andrea, Sara M. Giacomini, Carlo Corbetta, Maria Teresa Landi, Matteo Bonzini, Dario Consonni, Paolo Grillo, Donald G. Patterson, Angela C. Pesatori, and Pier Alberto Bertazzi. 2008. Neonatal thyroid function in Seveso 25 years after maternal exposure to dioxin. PLoS Medicine 5(7): e161.1549-1277http://nrs.harvard.edu/urn-3:HUL.InstRepos:4556467Background: Neonatal hypothyroidism has been associated in animal models with maternal exposure to several environmental contaminants; however, evidence for such an association in humans is inconsistent. We evaluated whether maternal exposure to 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a persistent and widespread toxic environmental contaminant, is associated with modified neonatal thyroid function in a large, highly exposed population in Seveso, Italy. Methods and Findings: Between 1994 and 2005, in individuals exposed to TCDD after the 1976 Seveso accident we conducted: (i) a residence-based population study on 1,014 children born to the 1,772 women of reproductive age in the most contaminated zones (A, very high contamination; B, high contamination), and 1,772 age-matched women from the surrounding noncontaminated area (reference); (ii) a biomarker study on 51 mother–child pairs for whom recent maternal plasma dioxin measurements were available. Neonatal blood thyroid-stimulating hormone (b-TSH) was measured on all children. We performed crude and multivariate analyses adjusting for gender, birth weight, birth order, maternal age, hospital, and type of delivery. Mean neonatal b-TSH was 0.98 μU/ml (95% confidence interval [CI] 0.90–1.08) in the reference area (n = 533), 1.35 μU/ml (95% CI 1.22–1.49) in zone B (n = 425), and 1.66 μU/ml (95% CI 1.19–2.31) in zone A (n = 56) (p < 0.001). The proportion of children with b-TSH > 5 μU/ml was 2.8% in the reference area, 4.9% in zone B, and 16.1% in zone A (p < 0.001). Neonatal b-TSH was correlated with current maternal plasma TCDD (n = 51, β = 0.47, p < 0.001) and plasma toxic equivalents of coplanar dioxin-like compounds (n = 51, β = 0.45, p = 0.005). Conclusions: Our data indicate that environmental contaminants such as dioxins have a long-lasting capability to modify neonatal thyroid function after the initial exposure.en-USdiabetes and endocrinologypublic health and epidemiologypublic healthenvironmental healthendocrinologyJournal Article2010-11-1610.1371/journal.pmed.0050161