Thyroid and reproductive hormones in relation to pesticide use in an agricultural population in Southern Brazil

This study aimed to assess the association of short- and long-term exposure to pesticides with circulating levels of thyroid and reproductive hormones in an agricultural population in the South of Brazil. Serum specimens from 122 male and female adults residing in small agricultural properties were sampled both in the low and high pesticide use season. A comprehensive questionnaire was used to collect detailed information on recent and cumulative lifetime use of pesticides and other agricultural-related exposures. The difference in serum hormone levels between seasons was assessed by the T-test and Wilcoxon test for paired samples, and associations between pesticide exposure-related variables and hormone values were explored by multivariate linear regression analysis. Levels of total thyroxine (T4) and male testosterone were significantly reduced from the low to high pesticide use season. In the high exposure season, recent use of dithiocarbamate fungicides, not using full personal protection equipment, and use of manual equipment was associated with reduced levels of thyroid-stimulating hormone (TSH). Moreover, recent use of lambda-cyhalothrin (pyrethroid) was associated with reduced total T4 and increased male luteinizing hormone (LH), use of paraquat (herbicide) with reduced free triiodothyronine (T3), and use of phthalamide (fungicide) with increased male LH. We also found associations of lifetime years of agricultural work with reduced total T4 and increased male testosterone; and of lifetime agricultural work and use of various pesticide classes (i.e. insecticides, herbicides, organophosphate insecticides, dithiocarbamate fungicides, and pyrethroids), mancozeb (fungicide), and paraquat with slight changes in free or total levels of T4 and/or T3. Findings suggest that both short- and long-term exposure to agricultural pesticides may alter thyroid hormones and male testosterone levels among farm residents.