Phthalates, BPA may alter the body's thyroid hormone levels

Researchers have announced that exposure to phthalates or bisphenol A (BPA), which are common industrial chemicals, may alter thyroid hormone levels and potentially aggravate or even lead to thyroid disease.

A study published in the journal Environmental Health Perspectives found that individuals with higher measured amounts these substances, especially phthalates, in their urine tended to have abnormal levels of thyroid hormones, thyroglobulin or thyroid-stimulating hormone in their blood streams.

The report, the first large-scale, human-based study of its kind, suggested that these chemicals may interfere with the proper functioning of the thyroid gland.

Phthalates and BPA have already been labelled the potential causes of a number of serious health conditions, which is one reason why their production and distribution are more tightly regulated than in years past.

The Environmental Working Group (EWG) reports that phthalates are known disruptors of animal endocrine systems. Chemicals in this group are known as "plasticizers," since they make certain plastics more resilient and bendable when added during their production.

The EWG notes that phthalates have been found to reduce sperm counts or cause testicular atrophy, birth defects or even liver cancer in laboratory animals. As such, the Environmental Protection Agency classifies phthalates as pollutants.

BPA has a similar track record. The Centers for Disease Control and Prevention recently found that 93 percent of tested Americans had detectable levels of the substance in their urine.

Studies have shown that BPA may cause birth defects, much like phthalates. Unfortunately, this chemical is found in many products that use polycarbonate plastics, like compact disc cases, water bottles, aluminum cans, baby bottles and surgical tools, according to the National Institute of Environmental Health Sciences.

As a result, many public health experts recommend that people, particularly pregnant mothers, try to avoid food and beverage containers that have been made with BPA.

However, staying away from such things can be difficult. In the new study, researchers found that many participants had measurable levels of both chemicals in their urine. The presence of these substances appeared to have an effect that varied by age but was stronger for phthalates than BPA.

For instance, in both adolescents and adults, greater amounts of di(2-ethylhexyl) phthalate (DEPH) in the urine were associated with less triiodothyronine (T3) and thyroxine (T4), two of the body's primary thyroid hormones. Likewise, adults with more DEPH in their systems had lower levels of thyroglobulin, a protein used as a building block for the production of T3 and T4.

However, more DEPH in teens' urine indicated increases in T3, not decreases. Furthermore, thyroid-stimulating hormone - a chemical messenger that the brain uses to activate the thyroid gland - was more abundant in teens with higher DEPH levels.

The research team concluded that phthalates may interfere with healthy thyroid function. This confirms previous research published in the Journal of Health Sciences, which found that phthalates depressed thyroid hormone production in rats.

When thyroid hormones dip too low, an individual may be diagnosed with hypothyroidism, a condition afflicting roughly 5 percent of Americans, according to the National Institute of Diabetes and Digestive and Kidney Diseases.
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