iThyroid.com

PESTICIDES

Pesticides may have a chronic mineral depleting effect on humans and the end result could be thyroid disease. The following article indicates that Glyphosate preferentially binds to copper, probably making the copper less available. Glyphosate is extensively used in agriculture and is the pesticide in Montsano's Roundup.

An article in the L.A. Times (Sunday, July 1, 2001) indicated that 2/3 of the soybean crop in the U.S. and probably the majority of many food crops are grown with Roundup. If you look in the Parkinson's file, you'll see a study where a worker who accidentally doused himself with Glyphosate developed Parkinson's about a month later.

Because of the extensive use of this chemical, it's important to get additional information on the possible connection between residues of this chemical in our foods and the etiology of thyroid disease.

 

Chemosphere 2000 Jan;40(1):103-7

Glyphosate adsorption on soils of different characteristics. Influence of copper addition.

Morillo E, Undabeytia T, Maqueda C, Ramos A.

Instituto de Recursos Naturales y Agrobiologia (CSIC), Sevilla, Spain. morillo@irnase.csic.es

Results of glyphosate (GPS) adsorption on three soils of different characteristics show that the interaction of this pesticide with the soils was not related to their CEC and clay minerals content, but to the content of iron and aluminum amorphous oxides and organic matter. The presence of Cu in treatment solutions enhanced GPS adsorption, due to several reasons: GPS coordinates strongly to Cu, and Cu GPS complexes formed seem to have higher ability to be adsorbed on the soil than free GPS; GPS adsorption can take place on sites where Cu was previously adsorbed, acting as a bridge between the soil and GPS; when Cu was present the solution pH decreased, and GPS adsorption increased, since lower pHs lead to the formation of GPS species with lower negative charge, which are adsorbed more easily on the negatively charged soil surfaces.

PMID: 10665451 [PubMed - indexed for MEDLINE]

Maneb or mancozeb is manganese ethylenebisdithiocarbamate. This pesticide appears linked to the development of Parkinson's Disease. I'm wondering if it is also connected to thyroid disease. Possibly this is a source for high levels of manganese.

 

J Appl Toxicol 1997 Nov-Dec;17(6):369-75

Studies on rat thyroid after oral administration of mancozeb: morphological and biochemical evaluations.

Kackar R, Srivastava MK, Raizada RB.

Pesiticide Toxicology Laboratory, Industrial Toxicology Research Centre, Lucknow, India.

Mancozeb, an ethylenebisdithiocarbamate (EBDC), has been studied for its effects on rat thyroid. Single oral administration of mancozeb at different concentrations (9600, 12,000, 15,000 and 18,750 mg kg(-1) body wt) has derived the oral LD50 value as 15,000 mg kg(-1) body wt. in male rats. Mancozeb at repeated oral doses of 500, 1000 and 1500 mg kg(-1) day(-1) for periods of 30, 90, 180 and 360 days has produced dose-dependent signs of toxicity and death of animals. The fungicide caused a significant increase in thyroid/body weight ratio and histopathological changes. Reduced levels of thyroid radioiodine ([125]I) uptake, serum protein-bound iodine (PB[125]I), thyroxine (T4) and reduced activity of thyroid peroxidase (TPO) have also been observed after exposure to mancozeb. Thus, mancozeb has been shown to produce marked structural and functional changes in thyroid of rats.

 

 

Environ Health Perspect 1997 Oct;105(10):1126-30

Thyroid hormones and cytogenetic outcomes in backpack sprayers using ethylenebis(dithiocarbamate) (EBDC) fungicides in Mexico.

Steenland K, Cedillo L, Tucker J, Hines C, Sorensen K, Deddens J, Cruz V.

National Institute for Occupational Safety and Health, Cincinnati, OH 45226, USA.

Ethylenebis(dithiocarbamate) (EBDC) fungicides are used heavily in the United States. EBDCs (e.g., mancozeb, maneb) are metabolized to ethylene thiourea (ETU). The EPA classifies ETU as a carcinogen, based on thyroid and other cancers in rodents, and has restricted the use of EBDCs, while requiring workers to use protective equipment. There are no data on the potential carcinogenicity of EBDCs in humans, and there is only one study on human genotoxicity. ETU is known to cause decreases of thyroxine (T4) and increases in thyroid-stimulating hormone (TSH) in rodents. We have studied cytogenetic outcomes and serum thyroid hormone levels among 49 heavily exposed workers without protective equipment spraying EBDC on tomatoes in Mexico. We also studied 14 lightly exposed landowners and 31 nonexposed controls. Urinary ETU was used to compare exposure between groups. We found an increase in TSH (p = 0.05) among applicators compared to controls, but no decrease in thyroid hormone (T4). We found increases in sister chromatid exchange (p = 0.03) and in chromosome translocations (chromosome aberrations that persist through cell division) for applicators compared to controls (p = 0.05). However, the subset of reciprocal translocations showed a lesser increase (p = 0.24). Our data suggest that EBDCs affect the thyroid gland and the lymphocyte genome among heavily exposed workers. However, our data are limited to subclinical outcomes, are of borderline statistical significance, and should be interpreted with caution

The following study is very interesting because it indicates that some very commonly used fungicides inhibit TSH production. We see in many hypers that TSH does not recover once thyroid hormone levels drop. What if maneb and zineb inhibited TSH production, thyroid hormone levels dropped, and the immune system has to replace the TSH by directly stimulating the thyroid follicles into producing thyroid hormone? Perhaps this is one way to cause Graves' disease.

 

Arch Toxicol Suppl 1985;8:253-8

The effect of maneb, zineb, and ethylenethiourea on the humoral activity of the pituitary-thyroid axis in rat.

Laisi A, Tuominen R, Mannisto P, Savolainen K, Mattila J.

Ethylenebisdithiocarbamates (EBDCs) maneb and zineb are widely used fungicides the final metabolite of which is ethylenethiourea (ETU). EBDCs distort the humoral activity of the thyroid gland, and ETU is especially active in this respect. Male Wistar rats were exposed either to exogenous (100 ng i.p.) or endogenous (+4 degrees C) TRH stimulation. ETU (100-500 mg/kg i.p.) caused no changes in serum TSH levels whereas zineb (70-500 mg/kg i.p.) significantly decreased the bursts induced by cold or exogenous TRH. Maneb (20-200 mg/kg i.p.) significantly decreased the cold-induced TSH response while it had no effect on the TRH-stimulated TSH secretion. None of the agents caused significant changes in serum T3 or T4 levels. It seems that maneb, and zineb, but not ETU, inhibit rat TSH secretion through an action on the endogenous TRH at the hypothalamic or pituitary level. The mechanism behind this action may be the inhibition of dopamine-beta-hydroxylase.