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Pesticide use and incident hyperthyroidism in farmers in the Agricultural Health Study
  1. Srishti Shrestha1,
  2. Christine G Parks1,
  3. Whitney S Goldner2,
  4. Freya Kamel1,
  5. David M Umbach3,
  6. Mary H Ward4,
  7. Catherine C Lerro4,
  8. Stella Koutros4,
  9. Jonathan N Hofmann4,
  10. Laura E Beane Freeman4,
  11. Dale P Sandler1
  1. 1 Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
  2. 2 Department of Internal Medicine, Division of Diabetes, Endocrinology, and Metabolism, University of Nebraska Medical Center, Omaha, Nebraska, USA
  3. 3 Biostatistics and Computational Biology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
  4. 4 Occupational and Environmental Epidemiology Branch, National Cancer Institute, Rockville, Maryland, USA
  1. Correspondence to Dr Dale P Sandler, Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NA 27709, USA; sandler{at}


Background Few studies have evaluated associations between pesticides and hyperthyroidism.

Objective We evaluated associations between specific pesticides and incident hyperthyroidism in private pesticide applicators in the Agricultural Health Study.

Methods We used Cox proportional hazards models to estimate HRs and 95% CIs for associations between pesticide use at enrolment and hyperthyroidism (n=271) in 35 150 applicators (mostly men), adjusting for potential confounders.

Results Ever use of several pesticides (organophosphate insecticide malathion, fungicide maneb/mancozeb, herbicides dicamba, metolachlor, and atrazine in overall sample and chlorimuron ethyl among those ≤62 years) was associated with reduced hyperthyroidism risk, with HRs ranging from 0.50 (95% CI 0.30 to 0.83) for maneb/mancozeb to 0.77 (95% CI 0.59 to 1.00) for atrazine. Hyperthyroidism risk was lowest among those with higher intensity-weighted lifetime days of using carbofuran and chlorpyrifos (ptrend ≤0.05).

Conclusions Observed associations between pesticides and decreased risk of hyperthyroidism warrant further investigation.

  • pesticides
  • hyperthyroidism
  • Agricultural Health Study

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  • Contributors All contributors meet the criteria for authorship.

  • Funding This work was supported by the Intramural Research Program of the National Institute of Health, National Institute of Environmental Health Sciences (Z01-ES-049030) and National Cancer Institute (Z01-CP-010119).

  • Competing interests None declared.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Requests for data, including the data used in this manuscript, are welcome as described on the Study Website ( Data requests may be made directly at; registration is required. The Agricultural Health Study is an ongoing prospective study. The data sharing policy was developed to protect the privacy of study participants and is consistent with study informed consent documents as approved by the NIH Institutional Review Board. Dr. Dale P Sandler is the NIEHS Principal Investigator of the Agricultural Health Study and is responsible for ensuring participant safety and privacy.