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
cellsThe cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos...
. It should be distinguished from
hyperplasiaHyperplasia is a general term referring to the proliferation of cells within an organ or tissue beyond that which is ordinarily seen . Hyperplasia may result in the gross enlargement of an organ, the formation of a benign tumor, or may be visible only upon histological analysis with a microscope...
, in which the cells remain approximately the same size but increase in number. Although hypertrophy and hyperplasia are two distinct process, they frequently occur together, such as in the case of the
hormonallyA hormone is a chemical released by one or more cells that affects cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms...
-induced proliferation and enlargement of the cells of the
uterusThe uterus is a major female hormone-responsive reproductive sex organ of most mammals, including humans. It is within the uterus that the fetus develops during gestation. The term uterus is used consistently within the medical and related professions; the Germanic term, womb is more common in...
during
pregnancyPregnancy is the carrying of one or more offspring, known as a fetus or embryo, inside the uterus of a female. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets. Human pregnancy is the most studied of all mammalian pregnancies. Obstetrics is the surgical field...
.
Muscular hypertrophy
One of the two most common and visible forms of organ hypertrophy occurs in skeletal muscles in response to
strength trainingStrength training is the use of resistance to muscular contraction to build the strength, anaerobic endurance and size of skeletal muscles. There are many different methods of strength training, the most common being the use of gravity or elastic/hydraulic forces to oppose muscle contraction...
(known as
muscle hypertrophyMuscle hypertrophy is the increase of the size of muscle cells. It differs from muscle hyperplasia, which is the formation of new muscle cells.- Muscular hypertrophy :...
). Depending on the type of training, the hypertrophy can occur through increased
sarcoplasmThe Sarcoplasm of a muscle fiber is comparable to the cytoplasm of other cells fluid of the muscle, but it houses unusually large amounts of glycosomes and significant amounts of myoglobin, an oxygen binding protein...
ic volume or increased
contractile proteinsThe sliding filament theory describes a process used by muscles to contract.-Process of movement:Myosin is a molecular motor that acts like an active ratchet. Chains of actin proteins form high tensile passive 'thin' filaments that transmit the force generated by myosin to the ends of the muscle. ...
.
Ventricular hypertrophy
Ventricular hypertrophyVentricular hypertrophy is the enlargement of ventricles in the heart. Although left ventricular hypertrophy is more common, enlargement can also occur in the right ventricle, or both ventricles.- Physiology :...
is the increase in size of the
ventriclesIn the heart, a ventricle is a heart chamber which collects blood from an atrium and pumps it out of the heart...
of the
heartThe heart is a muscular organ found in all vertebrates that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
. Changes can be beneficial or healthy if they occur in response to
aerobicAerobic exercise is exercise that involves or improves oxygen consumption by the body. Aerobic means "with oxygen", and refers to the use of oxygen in the body's metabolic or energy-generating process...
or
anaerobic exerciseAnaerobic exercise is exercise intense enough to trigger anaerobic metabolism. It is used by athletes in non-endurance sports to promote strength, speed and power and by body builders to build muscle mass...
, but ventricular hypertrophy is generally associated with pathological changes due to high blood pressure or other disease states.
Hypertrophy of the breasts
GigantomastiaGigantomastia is extreme growth of the breasts ; formally, it is bilateral benign progressive breast enlargement to a degree that requires breast reduction surgery to remove more than 4 lb of tissue on each side. Gigantomastia was first described in scientific literature in 1648...
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
pregnancyPregnancy is the carrying of one or more offspring, known as a fetus or embryo, inside the uterus of a female. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets. Human pregnancy is the most studied of all mammalian pregnancies. Obstetrics is the surgical field...
, but also with the more frequently juvenile gigantomastia during
pubertyPuberty is the process of physical changes by which a child's body becomes an adult body capable of reproduction. Puberty is initiated by hormone signals from the brain to the gonads . In response, the gonads produce a variety of hormones that stimulate the growth, function, or transformation of...
(
virginal breast hypertrophyVirginal breast hypertrophy is the common name for the medical condition juvenile macromastia and juvenile gigantomastia. This condition causes a woman's breasts to grow rapidly to an excessive weight during puberty. Breast hypertrophy in pregnancy is rare...
). Glutes also experience severe hypertrophy during the first stages of puberty
Hypertrophy of the clitoris
In the most pronounced cases, clitoromegaly is a symptom of intersexuality since the large clitoris resembles a penis (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).
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