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The Endocrine System


This section of the site focuses on the biological roles of the endocrine system, the ways in which chemicals can interact with the endocrine system and the huge complexity of the endocrine, immune and nervous systems and of the development of the body. These complexities make it very difficult to predict the influence of chemicals on the body.

1) The key hormones

The endocrine system is a complex interplay between a number of hormones, including the sex hormones the oestrogens and androgens, and other hormone systems such as the thyroid system. Oestrogens such as oestradiol (structure below) are the hormones that influence the development and maintenance of female sex characteristics, and the maturation and function of the sex organs. Chemicals which can imitate an oestrogen are known as oestrogenic chemicals. Androgens such as testosterone serve a similar purpose in males. The situation isn't as simple as this though; see the complexity page for more details.


2) Mechanisms of endocrine disruption

A hormone disrupting chemical can affect the hormonal system of an organism in a wide variety of ways, including imitating hormones, blocking their action and accelerating the breakdown of hormones. More details...

3)Other factors

There are many variables which affect whether a hormone disrupting chemical has a biological effect, including uptake, distribution, nature of action and time of action. More details...

4) The complexity of the endocrine, immune and nervous systems and human development

The development and functioning of the human - and animal - body depends on a complex interaction of chemicals, in which everything must happen at the right time.

Three crucial parts of the human body are the immune system, the hormonal system and the nervous system. It is easy to detect abnormalities in many other parts of the body - if you break your leg, or are bleeding, it is pretty obvious. Detecting changes in these systems is far harder. This is one of the reasons that providing proof of harm to any of these systems is difficult, unless the harm is very substantial - e.g. the damage to the immune system due to HIV. These three systems also affect each other, particularly during the development of the body.

Many of the interactions within and between these systems depend on fairly simple chemicals - all potential targets for imitation by man - made chemicals. The pharmaceutical industry deliberately produces chemicals that affect these systems - the chemical industry does it accidentally - Every chemical is potentially a pharmaceutical. More details...

This page was last updated in October 1999
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URL: http://website.lineone.net/~mwarhurst/endocrine.html