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Hypertrophy (from Greek ὑπέρ "excess" + τροφή "nourishment") is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It should be distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number. Although hypertrophy and hyperplasia are two distinct processes, they frequently occur together, such as in the case of the hormonally-induced proliferation and enlargement of the cells of the uterus during pregnancy.
Examples of hypertrophy
One of the two 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 the breasts
Gigantomastia is the extreme growth of the breasts, i.e. 10 pounds (5 kg) per breast and more. In severe cases it is possible for women to have breasts that weigh well in excess of 20 lb (9 kg) each. Gigantomastia can occur as a rare complication of pregnancy, but also with the more frequently juvenile gigantomastia during puberty (virginal breast hypertrophy).
Hypertrophy of the clitoris
In the most pronounced cases, clitoromegaly is a symptom of intersexuality since the large clitoris resembles an apple (the different grade of genital ambiguity is commonly measured by the Prader classification ranging, in ascending order of masculinisation, from 1: Female external genitalia with clitoromegaly through 5: Pseudo-phallus (looking like normal male external genitalia).