Editor-In-Chief: C. Michael Gibson, M.S., M.D. 
Hypertrophy is the increase of the size of an organ or in a select area of the tissue. It should be distinguished from hyperplasia which occurs due to cell division increasing the number of cells while their size stays the same; hypertrophy occurs due to an increase in the size of cells, while the number stays the same.
Examples of Hypertrophy
One of the most common and visible forms of organ hypertrophy occurs in skeletal muscles in response to strength training (known as muscle hypertrophy). Depending on the type of training, the hypertrophy can occur through increased sarcoplasmic volume or increased contractile proteins.
Ventricular hypertrophy is the increase in size of the ventricles of the heart. Changes can be beneficial or healthy if they occur in response to aerobic or anaerobic exercise, but ventricular hypertrophy is generally associated with pathological changes due to high blood pressure or other disease states.
Hypertrophy of breast
Gigantomastia is the extreme growth of the breasts, i.e. 10 pounds per breast and more. In severe cases it is possible for women to have breasts that weigh well in excess of 20 lb each. Gigantomastia can occur as a rare complication of pregnancy, but also with the more frequently juvenile gigantomastia during puberty (virginal breast hypertrophy).