21
Jul
Pesticide Exposure Linked to Thyroid Dysfunction and Thyroid Cancer, Literature Review Finds
(Beyond Pesticides, July 21, 2026) A literature review in Current Opinion in Endocrine and Metabolic Research highlights research connecting pesticide exposure to thyroid hormone alterations and thyroid carcinogenesis (cancer). Studies find that exposure to pesticides, whether through occupational, residential, or dietary routes, can lead to endocrine disruption, thyroid dysfunction, and neoplasia (tumor development). “With agriculture playing an essential role in meeting worldwide demands for food and fuel, it is not only important to continue to study both acute and chronic effects of pesticide exposure on thyroid function, both environmental and occupational, but it is also important to explore the impact on multi-organ systems and transgenerational toxicity,†the authors, from the University of Colorado Anschutz Medical Campus, state.
According to the American Thyroid Association, an estimated 20 million Americans currently have some form of thyroid disease, with more than 12% of the U.S. population expected to develop a condition during their lifetime. Women also face disproportionate risks, as they are five to eight times more likely than men to have thyroid problems. During her lifetime, one in eight women will develop a thyroid disorder. The American Association of Clinical Endocrinology explains that the thyroid gland, while relatively small, plays a large role in influencing the function of important organs, including the heart, brain, liver, kidneys, and skin. “The thyroid creates two hormones—triiodothyronine (T3) and thyroxine (T4)—that travel throughout your body to regulate blood pressure, body temperature, heart rate, metabolism and how the body reacts to other hormones,†they describe. Impacts on thyroid function thus have cascading effects throughout the body.
Background
Pesticide exposure can occur directly or indirectly, in the home or workplace or by encountering persistent pesticides present in the air, food supply, soil, or water. Many pesticides are also identified as endocrine disrupting chemicals (EDCs), which are any synthetic or natural compounds that hinder endocrine system functions and create harmful effects on organisms. These chemicals can impact the thyroid gland, which is vital in producing hormones and affects body functions.
The Endocrine Society’s Second Scientific Statement on EDCs identifies specific herbicides, insecticides, and fungicides as endocrine disruptors that can impact thyroid functioning. This is “likely due to the structural similarities between thyroid hormones and some EDCs.†Previous research has also connected specific pesticide exposures and thyroid carcinogenesis, highlighting the need to remove exposure routes to these harmful chemicals.
Literature Review Results
In reviewing recent scientific literature, focusing primarily on epidemiologic associations and in vivo studies in the last two to five years, the authors analyzed 15 articles related to pesticide exposure and thyroid function. The results include:
Epidemiological Studies on Thyroid Function
- One study, which conducts a meta-analysis of nine other studies, finds a significant association between occupational exposure to organochlorines, organophosphates, pyrethroids, and herbicides with hypothyroidism.
- A study in Ecotoxicology and Environmental Safety, using the U.S. National Health and Nutrition Examination Surveys (NHANES) 2007-2008 data with 1434 participants, compares single and mixed organophosphate exposures with thyroid hormone levels. The results show that organophosphate metabolites, including dimethylphosphate (DMP), diethylphosphate (DEP), dimethylthiophosphate (DMTP), diethylthiophosphate (DETP), and dimethyldithiophosphate (DMDTP), are associated with significantly decreased FT3 (free triiodothyronine) levels.
- In a retrospective cross-sectional study of pyrethroid and herbicide exposure and thyroid function alterations, a cohort of 60 hospitalized patients with pyrethroid poisoning “was found to have a significant decrease in FT4 [Free Thyroxine], TT4 [Total Thyroxine], Tg Ab [Thyroglobulin Antibody], and TPO Ab [Thyroid Peroxidase Antibody] compared to 60 healthy control participants.â€
- Another cross-sectional study, published in Environmental Research, investigates 144 environmental pollutants, including pesticides, and their effects on thyroid function. The results highlight certain organochlorines, organophosphates, and herbicides that are associated with significant decreases in hormone levels.
In Vivo Studies on Thyroid Function
- Thyroid hormone homeostasis is disrupted with pesticide exposures, as shown in research with zebrafish. One study that systematically reviews 42 studies “showed multiple insecticides and herbicides exposures were associated with different thyroid hormone alterations in zebrafish including increased T3 and T4 as well as decreased T4 levels.â€
- A study in Environmental Science & Technology finds alter thyroid gene expressions in tadpoles with exposure to the insecticide chlorpyrifos, showing how pesticides can disrupt thyroid hormone dependent development.
- A study of glyphosate-based herbicide (GBH) exposure links these chemicals to an increased risk of thyroid dysfunction in farmers. In investigating “the impact of GBH exposure on HPT axis in male rats from postnatal days into adult life,†the study finds “GBH exposure was significantly associated with increased T4, increased TSH receptor [receptor for thyroid hormone] transcription, decreased follicular diameter, and decreased Dio2, Thra1, and Thra2 [enzymes and receptors critical to thyroid hormone system] transcript expressions in the hypothalamus.â€
Thyroid Neoplasia
- A 20-year follow-up study of the Agricultural Health Study (AHS) cohort, “a prospective cohort of private pesticide applicators, their spouses, and commercial applicators in Iowa and North Carolina who have self-reported pesticide exposure data as well as longitudinal disease follow-up,†shows significantly increased relative standardized incidence ratios (RSIR) for thyroid cancer in AHS participants compared to the general population.
- A separate study using males with occupational pesticide exposure within the AHS finds “a significant association between self-reported usage of the fungicide metalaxyl and all thyroid cancers, and papillary thyroid cancer specifically.†The study also reports a significant association between the organochlorine insecticide lindane and all thyroid cancers.
- A case control study with data from the California Cancer Registry analyzes the association between residential exposure to 29 different pesticides in the 20 years prior to thyroid cancer diagnosis. “When evaluating 2,067 exposed individuals and 1,003 controls, they report significant associations between [the herbicides] paraquat, glyphosate, and oxyfluorfen.â€
- In Frontiers in Endocrinology, researchers connect pesticide exposure to epigenetic alterations that contribute to carcinogenesis. The study “evaluated the impact of several OCs [organochlorines] on tumor suppressor gene methylation [turning gene function off] and found significantly higher TSHR promoter methylation in papillary thyroid carcinoma (PTC) patients as compared to benign thyroid nodules and significantly lower P16 methylation in PTC patients compared to benign thyroid nodules.â€
Previous Coverage
Daily News, titled Literature Review Finds Heightened Risks for Thyroid Cancer in Women with Pesticide Exposure, examines a study in Ecotoxicology and Environmental Safety that finds a sex-specific relationship between pesticide exposure and thyroid cancer, with heightened risks for women. “This study aimed to elucidate the relationship between pesticide exposure and TC [thyroid cancer], focusing on insecticides, herbicides, and fungicides,†the authors state. In considering scientific literature on thyroid cancer and pesticide exposure by pesticide type to extract data and statistically analyze the link between exposure and risk of thyroid cancer, the results indicate a positive association between exposure to insecticides, herbicides, and fungicides and thyroid cancer, with the sex-based analysis revealing the risk of thyroid cancer is higher in females.
Another literature review, published in Endocrines, amasses hundreds of studies on EDCs that showcase adverse effects on growth, development, reproduction, and metabolism. The authors, a team of scientists and academics from Brazil, shed light on the link between EDC use and thyroid dysfunction, leading to increasingly prevalent illnesses and deadly diseases. “Several EDCs have been classified as thyroid disruptors, impairing thyroid hormone [TH] production, synthesis, metabolism, transport, and/or actions,†the researchers state. They continue: “[S]tudies have correlated th[e] rise in thyroid dysfunctions and cancers with increased exposure to EDCs. Although many EDCs are linked to thyroid dysfunction, this review focuses on the deleterious effects of plasticizers, organochlorine pesticides, and per- and poly-fluoroalkyl substances on thyroid function. These contaminants are commonly found in food, water, and everyday products.†(See Daily News Study Links Endocrine-Disrupting Chemicals to Thyroid Dysfunction with Grave Health Effects.)
Additional Daily News coverage on thyroid dysfunction and disease can be found here. To learn more about thyroid cancer, and all other types of cancer that can be linked to pesticide exposure, visit the Pesticide-Induced Diseases database on cancer here.
Moving Forward
Beyond Pesticides’ mission is to provide healthy air, water, land, and food for current and future generations by eliminating all petrochemical pesticides, including EDCs, and synthetic fertilizers by 2032. Beyond Pesticides also advocates for a precautionary approach in how land is managed, with organic agriculture and land management as the answer.
You can support this holistic solution by educating yourself through the Daily News Blog and the Pesticide-Induced Diseases Database, as well as buying or growing organic food. For more information on why organic is the right choice for both consumers and the farmworkers who grow our food, see Health Benefits of Organic Agriculture.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source:
Lin, J. and Goldner, W. (2026) The impact of pesticide exposure on thyroid function and neoplasia, Current Opinion in Endocrine and Metabolic Research. Available at: https://www.sciencedirect.com/science/article/abs/pii/S2451965025000249.
