What Is Hypertrophy? - Definition, Causes, Symptoms & Treatment

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  • 0:00 Definition of Hypertrophy
  • 1:45 The Good and Bad of…
  • 2:17 Physiologic Hypertrophy
  • 3:30 Pathologic Hypertrophy
  • 4:25 Signs, Symptoms, and Treatment
  • 5:05 Lesson Summary
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Lesson Transcript
Instructor: Lisa Miklush

Lisa teaches pathophysiology and pharmacology in baccalaureate and graduate nursing programs and has a PhD in nursing.

Hypertrophy is one of the ways cells grow to adapt to changes in their environment, and it can be both a good and a bad thing. In this lesson, learn about the types of hypertrophy, their causes, signs, symptoms, and treatments.

Definition of Hypertrophy

Hypertrophy is a term used to describe one of the ways cells—those tiny units that do important work in our bodies—adapt to environmental changes. Environmental changes can be things like hormonal stimulation, inflammation, or an increased workload.

Healthy cells keep us alive and fit. In order for our cells to stay healthy, the environment in which they live needs to be healthy, and the work they are expected to do needs to stay within normal limits. If there is a significant change in the environment, the cells will try to adapt to the situation so they can keep on working. One of the methods that cells use to adapt is by the process of hypertrophy.

Pictured here are five healthy cells of normal size, and below them are those same cells after they have changed into bigger cells.

Normal cells

Hypertrophied Cells

The bigger cells have become hypertrophied. If a cell increases in size beyond what is normal for that cell, then we can say that cell has undergone the process of hypertrophy. Whenever you see hyper in a word, think of the words 'excessive' or 'above'. Put this together with troph, which refers to stimulation from nutrition, hormones, or other growth factors, and you'll understand why hypertrophy refers to a cell that has grown bigger than normal.

Also, remember that cells have tiny organelles inside them that are the cell's internal machinery. As the cell grows in size, some of these organelles will increase in number in order to support the activities of the larger cell. For example, mitochondria, the cellular power generators, will increase in number to provide enough energy for the larger cell. The endoplasmic reticulum will increase to support the manufacturing processes of the cell, and proteins in the plasma membrane will increase in number as the cell hypertrophies.

The Good and Bad of Hypertrophy

Hypertrophy can be good or bad. Good types of hypertrophy are referred to as physiologic hypertrophy, and bad types of hypertrophy are referred to as pathologic hypertrophy. Hypertrophy can happen to many different types of cells throughout the body. So, what kinds of situations can cause cells—and, therefore, the organs and tissues that are made up of those cells—to undergo the process of hypertrophy? And, how can we tell if the hypertrophy is physiologic or pathologic? To find out, let's look at some examples.

Physiologic Hypertrophy

Let's say you want to build your biceps muscles in your arms and increase your muscle strength. To accomplish this, you begin a weight lifting program, and after several weeks, your bicep muscles are larger, and you are a lot stronger than you used to be. What happened? The weight lifting caused an increased workload on your muscles, and this stimulated the cells to adapt by getting bigger. This kind of hypertrophy is a normal, expected type of cellular adaptation to the increased workload. This normal type of hypertrophy is an example of physiologic hypertrophy. The physiologic hypertrophy of your biceps is characterized by normal structural changes of the muscle and enhanced strength and function.

Physiologic hypertrophy can also occur in the heart. The heart is a muscle, and it can also undergo hypertrophy when its workload is increased. Physiologic hypertrophy of the heart can occur in elite athletes, who participate in high-intensity training on a regular basis. In the case of the athlete, hypertrophy of the individual cells results in increased muscle mass, enhanced cardiac function, and greater endurance. It's important to note that physiologic hypertrophy is reversible, so when the exercise stops, the hypertrophy reverses and the cells return to their normal size.

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