title: Changes in retinol-binding protein concentrations and thyroid homeostasis with nonoccupational exposure to DDT.
abstract: BACKGROUND
  The 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.
  
  
  OBJECTIVE
  Our objective was to investigate the association between DDT uptake (as reflected in plasma concentrations) and thyroid homeostasis while considering related factors.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  RBP 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.
  
  
  CONCLUSIONS
  RBP 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.
authors.affiliation: Department of Chemical Pathology, School of Medicine, University of Pretoria, Pretoria, South Africa. rhena.delport@up.ac.za
authors.forename: Rhena
authors.initials: R
authors.lastname: Delport
authors.forename: Riana
authors.initials: R
authors.lastname: Bornman
authors.forename: Una E
authors.initials: UE
authors.lastname: MacIntyre
authors.forename: Nicholette M
authors.initials: NM
authors.lastname: Oosthuizen
authors.forename: Piet J
authors.initials: PJ
authors.lastname: Becker
authors.forename: Natalie H
authors.initials: NH
authors.lastname: Aneck-Hahn
authors.forename: Christiaan
authors.initials: C
authors.lastname: de Jager
mesh_terms: D000293:Adolescent; D000328:Adult; D003634:DDT / Q000097:blood* / Q000633:toxicity*; D006801:Humans; D008297:Male; D012177:Retinol-Binding Proteins / Q000378:metabolism*; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism*; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D055815:Young Adult
chemical_list: D012177:Retinol-Binding Proteins; D014284:Triiodothyronine; D003634:DDT; D013974:Thyroxine