Endocrine Disrupting Chemicals (EDCs)

Some background information on EDCs from major international bodies.

A Talk on endocrine disruptors by leading expert Thomas Zoeller

For those interested in a little more detail this is an excellent video. Prof Zoeller is an outstanding scientist, this is mainstream science. There are introductions and biography and the talk begins just after 7 minutes in. At around 37:10 there is mention of thyroid disruption with normal blood tests.

Notes on endocrine disruptors from the United States Government – The National Institute of Environmental Health Sciences (NIEHS)

World Health Organisation / United Nations Environmental Program

State of the science of endocrine disrupting chemicals – 2012

Endocrine experts united in disappointment with European Commission’s proposed criteria on EDCs

The European Society of Endocrinology (ESE) co-signed a joint letter with the Endocrine Society (ES) and the European Society for Paediatric Endocrinology (ESPE) to the European Commission expressing concern with the proposed criteria for the identification of Endocrine Disrupting Chemicals (EDCs).

We can see that EDCs are part of mainstream science. They have harmful effects on many hormone systems. This topic is championed by The Endocrine Society, the US NIEHS, WHO, UNEP and the European Society of Endocrinology.

In the topic on RTH we saw how a mutant receptor can bind to the Thyroid Response Element in preference to wild type (healthy) receptor and block hormone action. Mutant receptors also disrupt hormone action by other mechanisms. A mutant receptor is like but not quite the same as a wild type receptor. Endocrine disrupting chemicals are like but not quite the same as hormones.

Whilst there is great concern about EDCs I know of no studies that select a patient group, identify the EDC that causes their illness and finds a cure. This is the purpose of the Acquired Resistance to Thyroid Hormone (ARTH) topic.

If we look at the image below we can see that thyroid hormones are present in minute quantities, especially free T3. T3 has an elimination half-life of about a day. Many EDCs have much longer half-lives. For example, if EDC has a half-life of 100 days (not unusual) minute amounts would accumulate up to typical fT3 levels.

Clicking on the image that pops up will give a close up view.

A number of EDCs affect thyroid function. Some are such that human exposure is unlikely, others have a short half-life. Patients are likely to notice the effects of EDCs with short half-lives and take avoiding action. We look at EDCs with long half-lives and potential for human exposure, polybrominated diphenyl ethers (PBDEs) are the prime candidate.