Introduction to Endocrine Disrupting Chemicals

Negative Endocrine Health Outcome: Thyroid Disruption
Most studies of chlorpyrifos focus on its nervous system toxicity, but reports on its
effects on the thyroid hormone system are emerging, and suggest that chlorpyrifos
may be a risk factor for hypothyroidism. A chlorpyrifos metabolite was associated
with decreased thyroid stimulating hormone and increased T4 in men in one
study (120), and had the opposite association with these thyroid hormones of men
in another study (120). Experimental studies in animals also indicate that developmental
chlorpyrifos exposure alters the thyroid hormone system (121). Very
low prenatal chlorpyrifos exposure, below the level that produces any cholinergic
toxicity or behavioral changes, reduced brain thyroxine levels from early life into
adulthood in rats (121). This is consistent with several studies in mice demonstrating
that developmental chlorpyrifos exposure also decreased circulating thyroid
hormones in male and female mice (122, 123). Other actions of chlorpyrifos,
including neuroendocrine, estrogenic, and androgenic effects, have been reported.
B) CHEMICALS IN PRODUCTS
EDCs are found in many common-use, household, and personal products that
come into contact with the body or are around us in our home and work environments.
For example, children’s products, electronics, food contact materials,
personal care products, textile/clothing, and building products are regular parts of
daily life around the world (www.ipen.org/site/toxics-products-overview).
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