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.
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...
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...
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
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