Thyrotoxic effects of organophosphate insecticides in adults: a bibliometric and meta-analysis

Organophosphate insecticides (OPIs) are widely used worldwide, raising growing concerns over their potential thyrotoxic effects. Despite mounting evidence, inconsistencies persist regarding their impact on thyroid hormone (TH) regulation in humans. This study aimed to clarify the relationship between OPI exposure and TH levels in adults, addressing a critical gap in environmental health research.

A systematic literature search was conducted on Pubmed, Cochrane Library, Web of Science, and Google Scholar before 15th May 2025. After extraction, a bibliometric analysis was applied to synthetize the associations between OPIs and TH in adults; while a meta-analysis was performed to summarize epidemiological investigations with THs, including thyroid-stimulating hormone (TSH), total and free triiodothyronine (T3 and FT3), and total and free thyroxine (T4 and FT4).

From an initial pool of 852 articles, thirteen studies met the inclusion criteria for bibliometric analysis. Most were published between 1999 and 2024, with a peak in 2010, and originated primarily from the USA and Spain. Of these, seven studies, encompassing data from 6308 adults were included in the meta-analysis and grouped by five THs. The meta-analysis revealed significant negative associations in serum levels of T3 [β = - 0.02 (95% CI - 0.03, - 0.01)], and FT3 [β = - 0.02 (95% CI - 0.03, - 0.01)].

These findings highlight the potential endocrine-disrupting effects of OPI exposure in adults, particularly on the hypothalamic-pituitary-thyroid axis (HPT), and emphasize the need for continued investigation into the public health implications of such environmental exposures.