Is there a link between autism and glyphosate-formulated herbicides?

Abstract

Glyphosate is the most widely used herbicide on the planet, and its increasing use over time in the United States aligns well with the increasing rates of autism determined by the Centers for Disease Control. Based on the known mechanism of glyphosate toxicity, we hypothesize that a pregnant woman's exposure at midpregnancy to glyphosate-formulated herbicides (GFH) may produce, in her unborn child's brain, anatomic alterations of cortical neuron layering remarkably similar to those found in the brains of humans with autism. Glyphosate's known ability to chelate manganese ions combined with evidence of severely depleted serum manganese in cows exposed to glyphosate makes it likely that glyphosate would induce manganese deficiency in humans, interfering with the function of manganese-dependent enzymes. In particular, this would affect the maternal pituitary's manganese-dependent Protein Phosphatase 1 (PP1) enzyme, resulting in a significant reduction in maternal serum levels of Thyroid-Stimulating Hormone (TSH). A study of mid-pregnancy maternal TSH serum levels in human mothers has found a statistical correlation of reduced TSH to increased risk of autism in offspring. Since insufficient thyroid stimulation by TSH or by iodine deficiency would both induce hypothyroidism, effects of iodine deficiency can be expected to emulate effects of TSH deficiency. Cortical neuron disarrangements have been produced in the brains of offspring of rat dams fed an iodine-deficient diet, and such foci of disordered cortical neurons are characteristically found in human autistic brains. While the research literature on glyphosate's endocrine disrupting effects is limited, diverse evidence from animal studies reveals effects that suggest impaired thyroid function. If our hypothesis can be substantiated by a focused research effort, it would provide further justification for reducing or, ideally, eliminating glyphosate-formulated herbicide exposures in pregnant women.

Facts and Fallacies in the Debate on Glyphosate Toxicity

“…They extend this reasoning to multiple body functions to propose that the dysregulation of Mn utilization in the body due to glyphosate’s metal chelating properties explains autism, Alzheimer’s disease, Parkinson’s disease, anxiety disorder, osteoporosis, inflammatory bowel disease, renal lithiasis, osteomalacia, cholestasis, thyroid dysfunction, and infertility. More recently, Beecham and Seneff have used the same reasoning to conclude on a causative link between glyphosate chelation of Mn and the large rise in the incidence of autism spectrum disorders in children within the US ( 35 ). However, there are no scientific studies establishing a causative link between glyphosate and the described chronic diseases.…”

Disruption of urine metabolome and its interaction with gut microbiome by low-dose exposure of glyphosate-based herbicide in a rodent model

“…Although the effects of GBHs on human health are under intense public debate, evidence is emerging that they impact many health outcomes, including developmental and reproductive toxicity [36][37][38] , endocrine disruption 39,40 , host immunity [41][42][43] , obesity and diabetes 7,44 , gastrointestinal disorders 45 , cardiovascular disorders 46,47 and central nervous system dysfunction such as learning and memory impairment 48 , anxiety, depression 49 and autism 8 . These chronic health outcomes may occur even at doses lower than established risk safety guidelines, in particular during critical development windows as denoted in the DOHaD paradigm 50 .Environmental exposures may lead to changes in metabolism 18,51 .…”

“…However, current emerging evidence suggest that glyphosate or GBH such as Roundup, can adversely affect mammalian biology via multiple mechanisms [5][6][7][8] . Several studies have also suggested the possible link between GBHs exposure and abnormality in neurodevelopment 55,56 .…”

Genetics and epigenetics of autism: A Review

“…22,24 Furthermore, the increased use of the glyphosateformulated herbicide has also been associated with the increase in autism prevalence via its influence of the thyroid-stimulating hormone of pregnant women. 25…”