Neonatal TSH and maternal TCDD exposure in Seveso

Background and hypothesis. We evaluated neonatal thyroid function in a large population of women highly-exposed to 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a persistent and widespread environmental contaminant with established toxic effects including neonatal primary hypothyroidism in animal models. Methodology. 25 years after the Seveso, Italy accident of 1976, we conducted a population-based study on children born to the 1772 fertile-age women of the contaminated zones (A and B), and 1772 agematched women from the surrounding non-contaminated area (reference). Neonatal blood thyroidstimulating hormone (b-TSH) was measured at a single laboratory. Results. Mean b-TSH neonatal levels were 1.16 μU/ml (95%CI: 1.09-1.22) in the reference population, 1.61 μU/ml (95%CI: 1.50-1.72) in zone B, and 1.96 μU/ml (95%CI: 1.52-2.51) in zone A (ptrend< 0.001). Newborns from zone A and zone B had OR=6.6 (95%CI: 2.6-16.7; p<0.001) and OR=2.6 (95%CI: 1.4-5.2; p=0.005) respectively for the presence of b-TSH=>5 μU/ml, compared with the reference. An inverse relationship between b-TSH and time from the accident was found among siblings born from zone A (-1.01 μU/ml/year) and zone B mothers (-0.16 μU/ml/year). Siblings from the reference zone did not show a decrease (interaction test for zones p=0.004). Adjustment by gender, birth-weight and maternal age did not change the results. GEE models were used to handle potential correlation of b-TSH levels among siblings. Implications: Our findings indicate that maternal exposure to environmental contaminants such as TCDD produces effects on neonatal thyroid function that may occur far apart in time from the initial exposure.