Hypertrophy is a mechanism by which your body is able to adapt to changing conditions. Cells in your body have a normal size. Under stressed conditions, the cells may need to increase their function. The process by which they do this is known as hypertrophy.
Hypertrophy of cells and tissues is a common event in people. If you've ever lifted weights for gained muscle mass for any reason, you have made your muscles undergo hypertrophy. It is a common misconception that people gain more muscle tissue when they lift weights. In fact, what is really happening is simply a swelling of the muscles cells that are already there. You have the same number of cells, but each one is simply bigger. This is hypertrophy.
Gaining fat is another common example. When you eat too many cookies, your body responds by storing fat and other chemicals. This fat is processed and stored in the existing fat cells. The cells then become larger. It is very rare for new fat cells to be made, as there are generally plenty of preexisting cells in which to store the fat. The total number of cells stays the same.
One of the more dangerous medical conditions related to hypertrophy is known as ventricular hypertrophy. The ventricles are the two chambers of the heart that are responsible for pushing blood to your lungs and the rest of your body. As such, the muscle tissue in this part of the heart must be rather strong. After all, your heart never stops beating.
When you have and increase in the resistance to blood flow through your body, your heart has to push harder to get the blood to flow. Conditions such as obesity and high blood pressure can increase resistance to blood flow. When your heart is forced to work harder, the ventricles will compensate just like any other muscle by getting bigger.
Unfortunately, unlike having big muscles in your arms or legs, having a bigger than normal muscle in your heart is not a good thing. As the ventricle undergoes hypertrophy and gets bigger, it also stops working as efficiently. The increased size of the heart can cause obstructions to blood flow. It can also make the heart stiff and unable to fill properly. The initial compensation of hypertrophy can be a good thing, but if it gets too big, the heart will stop working properly. This can lead to heart failure.
Depending on the setting, hypertrophy can be a good thing, or it can be harmful. Ultimately, your cells have a normal size. Deviation too far from that normal size is not good.