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New study shows plastics inhibit thyroid hormone conversion

Plastics are now prevalent in everyday life and commonly contain endocrine-disrupting chemicals such as Bisphenol A (BPA). BPA is found in polycarbonate plastics which are used to make food and drink storage containers, in epoxy resins which coat the insides of food cans, bottle tops and water supply lines, in feminine sanitary products, in some dental sealants and composites, and even in the thermal paper that is used for many till receipts

Commonly referred to as an ‘endocrine-disruptor’, BPA is known to interfere with the way the body’s hormones work. It can enter the systemic circulation by leaching into food and drink, or can even be absorbed through the skin. Whilst more research is needed to understand the full impact of how BPA disrupts endocrine balance, individual studies are stacking up to build a very worrying picture.

A new study published in Hormone & Metabolic Research in October 2019 looked more specifically into the effects of plastics on key enzymes which convert thyroid hormones into their active forms.

This most recent study found BPA to have adverse effects on thyroid function.

The thyroid gland secretes mainly T4 (thyroxine) and this must be converted into T3 (triiodothyronine) in peripheral tissues. T3 is the most active form that the body can use. Type 1 and type 2 deiodinase enzymes are essential for this important conversion of T4 – T3 to take place.

In this latest animal study, researchers aimed to evaluate the effect of plastic endocrine disruptors on type 1 and type 2 deiodinase activities. They found Bisphenol A to be capable of inhibiting type 1 and 2 deiodinases and concluded that BPA can affect the peripheral metabolism of thyroid hormones and disrupt thyroid signalling.

This study is yet another good reason to do what you can to avoid Bisphenol A wherever possible. Read more here on how to protect your hormonal health by reducing your exposure to endocrine-disrupting chemicals such as BPA. 

1. Da Silva MM, Goncalves CFL et al. Inhibition of Type 1 Iodothyronine Deiodinase by Bisphenol A. Hormone & Metabolic Research 2019 Oct; 51(10): 671-677

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