Our body’s cells have an ability to adapt and even change in order to better tolerate and meet the demands placed on them. They have the capacity to increase or even decrease in size to meet the demands placed on them. When injured cells can even change from one cell type to another to avoid further injury. In the following, we will focus on changes in cell size.
The suffix -Trophy in medicine stands for growth. Its easy to remember this term when thinking about the trophies one receives when competing. Its always about winning the largest trophy.
Hypertrophy and hypotrophy are terms used to describe cell, tissue or muscle size. Hyper referring to an increase in size (like a champions trophy) and hypo referring to a decrease in size (like the small participation trophies you get just for trying).
Hypertrophy is seen commonly in overworked cells of the body. The muscles of a weight lifter is an example of a physiologic hypertrophy. Cardiac muscle of a patient with chronic hypertension can also undergo hypertrophic change, however, it’s a pathologic change due it’s originating from a disease. Hormonal change can also lead to changes in cell size. This occurs frequently in women during the menstrual cycle caused by hormonal fluctuations that lead to an increase and decrease in the size of the uterus (increase in size is also due to hyperplasia – an increase in the number of cells).
Hypotrophy can also be both physiologic and pathologic. Pathologic hypotrophy can occur when atherosclerosis develops plaques along the arterial walls slowly and gradually decreasing blood supply. These cells still have enough irrigation and oxygen supply to keep them viable but due to the decreased supply, they have a decreased cell function. This reduced capacity of the cell leads to a hypotrophic change. Physiologic hypotrophy can also be seen in the retired weight lifter who stopped working out. The stress on the muscle cells during each workout caused an increase in cell size, which also increases the number of organelles inside the cell allowing these cells to better tolerate the workouts. A cell can also decrease in size when a hormone that regulates its function is decreased or removed. This can occur in both pathologically and physiologically.
When the weight lifter mentioned earlier stops working out, the cells undergo a gradual hypotrophic change and eventually return to a normal size. However, if the muscle is not used at all for a long period of time, as in bone fractures that must be immobilized in a cast, the muscle can under go atrophy – a partial or complete wasting away of the tissue, muscle or organ. Another example of this can be seen in Senile Cerebral Atrophy (Senile referring to the elderly population) where areas of the brain begin to decrease in size and can lead to neurological symptoms.