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Roundup® the usual suspects: Could a weed killer cause hormonal imbalances in rats?

Pesticides are becoming a major health concern worldwide. Recently, Saudi Arabia, one of the major importers of green chillies from India issued a ban against this import citing high levels of pesticides in shipments. In a bizarre case in North India, five tigers were thought to have been killed by pesticides—DDT—between 2013 and 2015. Yet another story blames the widespread use of pesticides in Punjab as the main reason for rising cancer rates in the state.

Given the current extensive use of pesticides in agriculture and even in city gardens and playgrounds, concerns about the potential health risks of these chemicals need to be evaluated. Working towards addressing this matter, a group from the Indian Institute of Science (IISc), Bangalore, has tested the effects of a commonly used herbicide named Roundup® on hormonal balance in rats. In a recently published paper in the journal Toxicology Reports, Prof. Medhamurthy and his student Ms. Aparamita Pandey have found that Roundup® can cause imbalances in the synthesis of steroid hormones in male rats.

Roundup® marketed by Monsanto is the most extensively used herbicide. Roundup® kills weeds by inhibiting enzymes that synthesize aromatic amino acids (the basic building blocks that make up proteins) essential for plant development. Humans and most mammals do not have the enzymes for and therefore cannot synthesise these aromatic amino acids – which is why Roundup® is considered to be ‘safe’ and ‘non-toxic’. Recent studies, however, have suggested that Glyphosate, the primary constituent of Roundup® could be a carcinogen, affect the development of fetus and disrupt the hormonal function.

In males, the majority of steroid hormones are secreted by testis and the adrenal gland (hormone producing gland situated just above the kidneys). The corticosteroid hormones from the adrenal glands are vital not only for maintaining normal glucose and fat metabolism, but also for mineral balance in the body. The male hormone, testosterone, secreted from testis is essential for sexual functions. Secretion of corticosteroids and testosterone are controlled by the pituitary or ‘master gland’ that is found in the brain. Roundup® exposure at a dose as low as 10 mg per Kg body weight of rats causes decrease in testosterone and corticosterone secretions. The study uncovered that the effects of Roundup® seem to be caused by a decrease in the synthesis or release of the hormone ACTH (Adreno-Cortico-Tropic Hormone) from the pituitary gland. Without ACTH, the adrenal glands are not able to stimulate corticosterone hormone production. When rats exposed to Roundup® were injected with ACTH preparation, the deficiency of corticosterone was overcome.

“It is therefore highly possible that Roundup® affects other endocrine glands as well”, says Aparamita, first author of the study. “In this study we treated mice with Roundup® for only two weeks and we see such clear effects. Further investigations on longer exposure times should now be done as this weed killer is extensively used and humans are potentially exposed to it”, she adds.

The findings of this study are ominous since the research findings suggest that Roundup® interferes with the functioning of the pituitary or ‘master gland’ that controls the functioning of vital hormonal systems in the body. The current study draws a parallel between the observed effects of Roundup® treatment in rats to a condition known as ‘adrenal insufficiency’ in humans. Adrenal insufficiency is caused by abnormally low levels of cortisol that manifests as fatigue, anorexia, sweating, anxiety, shaking, nausea, heart palpitations and weight loss; chronic cases of which can be fatal, if untreated. Systematic studies to investigate the role of Roundup® exposure in adrenal insufficiency cases in humans are now warranted to validate that the formulation is truly ‘non-toxic’ to humans.

About the Authors:

Aparamita Pandey is a PhD student in Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science.

Medhamurthy Rudraiah is Professor at Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science.


Medhamurthy Rudraiah: ; 080-22933460

Aparamita Pandey: ; 080-22932490

The paper appeared in Toxicology Reports journal by Elsevier.