Histological Evidence of Thyroid Disruption in Wild Mice from Conventional and Organic Farming Environments

The main objective of this work is assessing the potential negative impact of organic farming on the thyroid gland and comparing it with the negative impact of conventional farming on this organ. Conventional farming practices deploy synthetic agrochemicals to maximize yields, many of which have endocrine-disrupting properties, like pesticides, while organic farming practices use natural alternative substances, favoring environmental sustainability and health protection. Studies suggest that organic farming yield can be contaminated with pesticide residues. Thyroid disruption underlies some of the most common endocrine pathologies worldwide. Previous studies have linked exposure to conventional farming with thyroid disruption; relatively less is known about effects of exposure to organic farming on the thyroid. Wild mice were selected as bioindicators, captured in a conventional farm (CF); an organic farm (OF), and two reference areas (RF’) without agriculture. Histomorphometric and histomorphological measurements of the thyroid were performed. Hypothyroidism signs were observed in mice exposed to either farming system, being less pronounced in organic farming-exposed mice: epithelium thickness, and the area and volume of epithelial cells were lower than in non-exposed mice [epithelium thickness (µm): 4.1617 ± 0.50860 (CF); 6.2825 ± 0.19308 (OF); 7.4605 ± 0.25412 (RF’)]. Histomorphologic alterations included lower follicular sphericity, irregularly-delimited epithelium, increased exfoliation into the colloid, and increased inflammation of thyroid tissue. Results suggest that, while organic farming might be a better alternative to conventional farming, it is not completely free of health hazards. Exposure to organic farming can cause thyroid disruption, with less pronounced effects. Although there are risks to be considered, results support the benefit of transitioning from conventional farming systems towards organic farming systems.