Although hormones tend to get a bad rap, they are in fact crucial to
the everyday functioning of the human body. Hormones are essentially chemical "messengers" that move through
the body directing complex processes such as growth, metabolism, and fertility. They can influence the immune
system and even have an effect on behaviour. From before a child is even born, hormones already play a central
role in their development, by guiding the brain and reproductive system. Simple things like converting food to
fuel, and going through puberty, would not be possible without hormones.
In response to a signal from the brain, hormones are directly released into the blood by the glands that produce
and store them. These glands are part of what is known as the endocrine system (endocrine means "secreting
internally"). Chemicals that disrupt the normal functioning of hormones are referred to as "endocrine disruptors".
The testes and ovaries are probably the most widely known of the
endocrine glands. In males, testes produce sperm and release the male
sex hormone testosterone; while in females, ovaries produce eggs and
the female hormone estrogen. These are the hormones that determine
sex characteristics such as muscle mass and the growth of facial hair.
They also aid in the production of sperm, as well as menstruation and
pregnancy. Other endocrine glands fulfill different functions. For
example the thyroid, pancreatic islets, and adrenal glands all play a
central role in growth, metabolism, and stress management.
All cells come into contact with hormones circulating in the bloodstream;
however only certain cells react to these hormones. A hormone's "target cells"
are specifically built with receptors for that hormone, so that they can respond
to its signal. When a hormone attaches to its receptor, it initiates a
biological reaction within the cell. So in some ways, hormone receptors can be
likened to a radio antenna that fields the signal produced by hormones. Without
the antenna, no signal can be received and the radio cannot function. This
process of signaling draws to a close when the circulating hormones are broken
down and excreted by the body.
The chemicals that disrupt hormones, or "endocrine disruptors," can break
the chain at any point along the hormone-signaling pathway. Some imitate the
hormone by binding to the receptor and sending a false signal that isn't from
the brain; and others block the processes of a natural hormone, preventing it
from binding to its receptor and having an effect. Endocrine disruptors can
also alter the amount of hormone synthesized, how fast it is broken down, and
the way in which a target cell reacts. These disturbances can disrupt the
development of an embryo, or even reduce an adult's ability to function properly.
So, in essence, hormones control almost every aspect of the body's functioning.
Hormones are tiny messengers that can have a disproportionately large effect on
the body, with the ability to make a person well or conversely bring about illness.
Hormones have an effect on every cell in the human body.
|
