What Are Hormones?, Hormone Deception, D. Lindsey Berkson

WHAT ARE HORMONES?

SIGNALS OF LIFE

Birds do it. Bees do it. Alligators and petunias, fruit flies and polar bears do it. The baby in the womb does it. A teenager with pink hair, a 100-year old woman blowing out her birthday candles, and an Olympian carrying the torch all do it. So do you and I. Every living thing that's bigger than one cell does it. Every organism operates through the same mechanism of signal and response that has changed very little over the last 400-500 million years or so.

One cell sends out a signal and another cell receives the message. It's so simple, yet this is how magic happens throughout biology – how life develops and gets directed.

The cell-to-cell signaling system was firmly established long before plants and animals split off from each other on the evolutionary path and it has remained basically the same ever since. This is called evolutionary conservation – meaning the signaling system has been basically the same throughout evolution. All life is based on sending and receiving these signals. The messages we are concerned with in this book are the ones in humans and animals that come from the endocrine system, called hormones.

When you think about it, life is about messages. What I am referring to here are the natural chemical messages that come from our genes and become the instructions for the next generation: how to grow, how to develop, how to mature from fetus to adulthood. These messages are life itself.
-- J. P. Myers

THE BODY'S MESSENGER SERVICE
The signal-response mechanism is used in many different ways in the body. Our immune, nervous and endocrine systems all work through this cell-to-cell process. These systems control development and aging – the way we grow from an embryo to a fetus to an infant to a child to a teenager to an adult, all the way to old age.

The endocrine system, which is responsible for sending out hormonal signals, runs a very efficient messenger service. An endocrine gland sends out a small amount of a hormone carrying an important message. The hormone jumps on its trusty bicycle and rides through the bloodstream until it finds the correct address – the cells of a specific organ or tissue (called target tissues) that are meant to receive the message. The hormone finds a place to park, called a receptor, located either at the cell surface or inside the cell, and delivers its message. The signal has been delivered from one cell to another.

Now there is a response. Central headquarters in the cell takes the message and runs with it. The message is copied and translated into orders which are sent to various parts of the body. For example, the pituitary is an endocrine gland that sends out a particular hormone signal which is received by the cells in the uterus and, in response, the uterus sheds its lining.You suddenly realize why your daughter has been eating candy bars and slamming doors for the past few days.

ANCIENT CELL PHONES

If the endocrine system is the body's messenger service, the hormone itself delivers the actual message. Hormones "urge" the body to regulate, through the action of the genes, among other things:

metabolism (the extraction of energy from nutrients),
sexual development and reproduction, o mental processes,
growth and maintenance, and many aspects of our development before birth.

Development is a word you will read frequently in this book. In humans and mammals, it refers to the growth and basic processes that take place, from the fertilization of the egg by the sperm through the entire step-by-step course of evolving into a mature living being. In a developing fetus, the endocrine system regulates cell division (growth) and organ differentiation (cell specialization) – the basic processes that set the stage for who we will become – and affects all parts of the body, including the brain.

It's a very competent and effective set-up. Messages are sent and received and the body complies with the orders contained in the messages. It's a system that's worked exceedingly well for a very long time.

Up until recently.

GETTING THE WRONG MESSAGE
For the last fifty years, man-made chemicals used in the external world have been entering our bodies, where they are participating in an age-old signal/response system that has not had time to adapt to these recently synthesized chemicals. Hormonal signals always used to come from inside our bodies or from natural substances, such as the estrogens in plants, that have evolved along with us.

Our bodies haven't had enough time to take into account these alien messengers, coming from outside our bodies, which are now pervasive in air, land, and water, and to make the necessary evolutionary changes that would protect us from these substances.

If something is wrong with the signal, the body will respond to the wrong message. In other words, an unnatural signal may create an inappropriate response. What science is discovering is that hormone disruptors can bind with receptors and send messages the same way our natural hormones can, but these particular messages can alter normal cell function and growth.

In fact, hormone disruption may very well turn out just be the tip of the iceberg when we finally learn how chemicals from the environment are acting inside the integrated whole of our bodies. In a machine, if one part is damaged or altered, the functioning of the entire engine can be disrupted. If someone threw a wrench into the engine of your beautiful new Jaguar, chances are your automobile would have trouble. Likewise, an incorrect message sent by a chemical that mimics a hormone can tell the genes to turn on when they should be turned off, or vice versa. Creating a disturbance at any one point can throw things off balance anywhere else in the body.