DDT breakdown chemical alters thyroid hormone function in pregnant women.

Jun 30, 2009

Lopez-Espinosa, MJ, E Vizcaino, M Murcia, S Llop, M Espada, V Seco, A Marco, M Rebagliato, JO Grimalt and F Ballester. 2009. Association between thyroid hormone levels and 4,4′-DDE concentrations in pregnant women (Valencia, Spain). Environmental Research doi:10.1016/j.envres.2009.02.003.

Synopsis by Jonathan Chevrier, Ph.D.

Researchers report that a woman's DDE exposure during early pregnancy is associated with altered thyroid hormone levels, a condition that could affect fetal brain development.

Pregnant women with higher blood levels of a long-lived pesticide residue were more likely to have skewed thyroid hormone levels, finds a study conducted in Spain.

Researchers found that women with higher DDE blood concentrations were 2.5 times more likely to have high thyroid-stimulating hormone (TSH). Increasing DDE exposure was also associated with reduced thyroxine (T4) levels.

Potential effects of chemicals on thyroid function during pregnancy are of concern because thyroid hormones play a crucial role in fetal brain development. Previous reports found high TSH and low T4 in pregnant women to be associated with reduced cognitive abilities in children aged between 10 months and 8 years.

DDE is a residue – or breakdown product – of the pesticide DDT. The insecticide was widely used for agricultural and public health purposes in the United States until the 1970s, when its use and production was banned by the Environmental Protection Agency. It was banned internationally following the 2001 Stockholm Convention on Persistent Organic Pollutants with an exception for malaria control. 

DDE and thyroid hormone were measured in blood collected from 157 women during the 12th week of pregnancy. Researchers also measured the concentration of PCBs in maternal blood but contrary to some reports previously published, found no associations with thyroid hormone levels.