What is a Hormone?
Hormones are molecules that are made by our bodies. To understand how hormones work, imagine that each hormone molecule is assembled from a bunch of Legos. As we look at the different hormones, we realize that they are all made from the same number of Legos, but that each hormone is shaped slightly differently. For example, all testosterone molecules are shaped exactly alike, but testosterone molecules are shaped slightly differently from estrogen molecules.
It turns out that shape is extremely important for hormone molecules, because shape is how cells tell which hormones to let in, and which ones to keep out. One part of each hormone molecule is shaped perfectly to fit inside a special lock, called a receptor. If a cell has this lock on the outside of it, the hormone can open the lock and get inside the cell. Once inside the cell, the hormone can begin to signal the cell to do something.What the hormone signals the cell to due usually depends on the type of cell it gets inside. A testosterone molecule inside a fat cell may signal that cell to do one thing, but the same testosterone molecule inside a muscle cell will tell it to do something else.
Hormones regulate how cells repair themselves, how they use or store nutrients like fat and sugars, how much and what kinds of protein they make, and how each cell interacts with neighbor cells. Each hormone molecule also has a special deactivate button on it. This button allows other molecules with the correct shape, called enzymes, to either take apart the hormone completely, or change its shape into another hormone that is needed. How much of an effect a hormone has on the body depends on how easily it can get inside cells, and how long it gets to stay active inside cells before an enzyme changes it into something else or takes it apart.
Since hormones affect many cells in the body, small changes in their levels can add up to big changes for the body. To see how this works, imagine that hormones are like traffic lights. When the hormone is inside the cell it gives that cell a green light, and if there is no hormone inside a cell, that cell has a red light. Just like city traffic lights, the body functions best when green lights and red lights are coordinated to let traffic flow smoothly. If one traffic light malfunctions and has red lights in both directions, it causes some disruption at that intersection, but the rest of the city traffic continues on without trouble. However, imagine that ALL the traffic lights across a city were malfunctioning. The entire city would be in chaos. Thus, the overall level of each hormone is important, but the balance between hormones is important also.