Acute Changes in Thyroid Hormone Levels among Thai Pesticide Sprayers.

Pornpimol Kongtip,Jutharak Yimsabai,Susan Woskie,Chavisa Phommalachai,Noppanun Nankongnab,Nattagorn Choochouy,Pajaree Konthonbut,Phanthawee Khangkhun,Sumate Pengpumkiat,Jutamanee Chungcharoen,Preecha Sowanthip,Nichcha Kallayanatham,Ritthirong Pundee

doi:10.3390/toxics9010016

Abstract

The objective of this study was to investigate the relationship of acute pesticide exposures and acute changes in thyroid hormones among Thai farmers. We recruited 78 farmers, who were scheduled to spray insecticides (chlorpyrifos and/or cypermethrin) or herbicides (paraquat and/or glyphosate). On the day before spraying, farmers collected their first morning void urine and went for blood collection. On the spray day, urine samples were collected at end of the spraying event and they were interviewed with questionnaires. The next morning, the first morning void urine and blood samples were collected. Blood samples were analyzed for thyroid hormones. Urine samples were analyzed for the metabolites of the pesticide sprayed. The results showed that the thyroid hormones, free triiodothyronine (FT3) and total triiodothyronine (T3) were significantly reduced as urinary chlorpyrifos metabolite increased the day after spraying. Total thyroxine (T4) significantly increased as cypermethrin metabolites increased the day after spraying. T4 significantly increased as urinary glyphosate levels increased; however, FT3 and T3 decreased significantly as urinary paraquat levels increased the day after spraying. These findings suggest that acute exposures to the pesticides chlorpyrifos, cypermethrin, paraquat and glyphosate can produce acute effects on the hypothalamic–pituitary–thyroid (HPT) axis, acutely altering thyroid hormone levels.

Highlights

This article is an open access articleOver 120 pesticides have been listed as potential endocrine-disrupting chemicals (EDCs) [1,2,3]
We have previously shown in the larger longitudinal cohort, from which the farmers in this study were recruited, that after adjusting for covariates, thyroid hormone levels of conventional pesticide using farmers were significantly higher than those of organic farmers
The field staff set an appointment with the farmers when they planned to spray chlorpyrifos, cypermethrin, paraquat or glyphosate in their fields

Summary

Introduction

This article is an open access articleOver 120 pesticides have been listed as potential endocrine-disrupting chemicals (EDCs) [1,2,3]. Many insecticides are considered EDCs, including organophosphates (OPs) such as chlorpyrifos-methyl and malathion, and pyrethroids such as cypermethrin, deltamethrin and permethrin. Alter thyroid hormone levels by disrupting central regulation, iodine uptake, production and distribution of thyroid hormones, or binding of the thyroid hormones to membrane transporters or receptors [4,5,6]. Several epidemiologic studies have established an association between OPs and alterations of thyroid hormone levels [8,9]. A limited number of studies have examined whether ever using OP pesticides was associated with hypothyroidism [9,10,11], or whether use in the past growing season was related to alterations in thyroid hormone levels [12,13,14]. Experimental animal studies have shown that organophosphate (OP) disturb thyroid gland function [15,16]

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