Changes in Retinol-Binding Protein Concentrations and Thyroid Homeostasis with Nonoccupational Exposure to DDT

Abstract

BackgroundThe insecticide dichlorodiphenyltrichloroethane (DDT) has been used for malaria vector control in the northern and eastern parts of the Vhembe District of Limpopo Province, South Africa, since 1945. Bioaccumulation of DDT raises concern because it reportedly affects thyroid function.ObjectiveOur objective was to investigate the association between DDT uptake (as reflected in plasma concentrations) and thyroid homeostasis while considering related factors.MethodsWe compared dietary intake, serum retinol-binding protein (RBP), transthyretin (TTR) and albumin concentrations, and liver and thyroid function between cases with evidence of a body burden of DDT in the circulation (concentration of any DDT isomer ≥ 0.02 μg/g lipid; n = 278) and controls (concentration of all DDT isomers < 0.02 μg/g lipid; n = 40) in a cross-sectional study. Further analyses were performed to assess the relevance of changes in RBP status associated with DDT uptake.ResultsRBP concentrations below the reference range were more prevalent in cases (54% vs. 10% in controls; χ2 = 27.4; p < 0.001), which could not be explained by nutrient intake. We observed significantly lower thyroid hormone concentrations among cases (p ≤ 0.01). We also observed a significant linear trend for serum concentrations of free thyroxine and free triiodothyronine (p < 0.001) and a significant quadratic trend for serum thyroid-stimulating hormone (p = 0.025) and TTR (p < 0.001) across the control group and case groups with normal and relatively low RBP concentrations. Relatively low RBP concentrations were associated with significantly higher DDT and 1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene (DDE) isomer concentrations and with a higher DDE/DDT ratio (p ≤ 0.01), which signifies long-term exposure. Inadequate intake of vitamin A and zinc were observed in 84% and 58%, respectively, of the total study population.ConclusionRBP concentrations appear to decrease in the presence of long-term DDT uptake, which may have deleterious effects on thyroid function and vitamin A nutritional status. This is of major concern in a population with poor vitamin A and zinc intake.

High levels of DDT in breast milk: Intake, risk, lactation duration, and involvement of gender

“…It is especially the first-born infants that will be exposed to higher ΣDDT levels; therefore experiencing greater risk when compared with their sibs. Research conducted in the same region as Dididi identified DDT-associated effects on male urogenital parameters and reduction of retinol binding protein (Aneck-Hahn et al, 2007;De Jager et al, 2009;Bornman et al, 2010;Delport et al, 2011).…”

Estimation of human body concentrations of DDT from indoor residual spraying for malaria control

“…Recent studies from South Africa found reduced retinol-binding protein and thyroid hormone concentration, urogenital malformations in newborn boys, and impaired semen quality, associated with non-occupational exposure to DDT (Aneck-Hahn et al, 2007;Bornman et al, 2010;Delport et al, 2011).…”

Effects of polychlorobiphenyls, polybromodiphenylethers, organochlorine pesticides and their metabolites on vitamin A status in lactating grey seals

“…Little is known about mechanisms of action of DDXs on vitamin A status. Delport et al (2011) showed that long-term DDT uptake reduced RBP concentrations in human blood.…”

“…Studies on laboratory and wild animals generally report depleted hepatic and adipose tissue retinoid stores as well as increased levels in the kidneys (Zile, 1992;Håkansson et al, 1994;Hallgren et al, 2001;Nyman et al, 2003;Ellis-Hutchings et al, 2006;Mos et al, 2007;Nová k et al, 2008). In plasma, both an increase and a decrease of vitamin A levels have been observed, probably depending on the species, the physiological state and the concentrations at which the animals were exposed (Zile, 1992;Nyman et al, 2003;Nová k et al, 2008;Cesh et al, 2010;Delport et al, 2011).…”