Human growth hormone is a protein that acts as a chemical messenger and it is responsible for a variety of vital functions in humans.  Most vertebrates have a form of growth hormone, often abbreviated as GH, while the human version is often abbreviated as hGH for human growth hormone.  Human growth hormone is also known as somatotropin. 

Somatotropin is produced by the ‘somatotrope’ cells of the anterior pituitary gland, and its secrection into the blood is controlled by chemical signals from the nearby hypothalamus gland.  Both the pituitary and hypothalamus glands are located in the middle of the brain.  Human growth hormone is quite large compared to most hormones, consisting of 191 amino acids.

Somatotropin plays a crucial role in stimulating cell growth and reproduction, and is at its peak levels in humans at adolescence, when much of a person’s growth is occurring.  Human growth hormone continues to play an important role throughout adult life, however.  It is released in small amounts during sleep, and helps to control cellular repair, metabolism, muscle growth and the maintenance of normal brain function.  It also helps to boost the immune system.

Human growth hormone is a very powerful protein, too much or too little of it can lead to a number of serious conditions.  A tumor in the pituitary gland can result in too much hGH, which can eventually lead to the condition known as ‘acromegaly’.  Acromegaly involves thickening digits, impinged nerves, blurred vision, and sometimes a form of diabetes.  If the tumor is removed, the effects of acromegaly can normally be reversible, however if the tumor occurred during childhood an abnormal amount of permanent growth may happen.  This is sometimes referred to as ‘gigantism’.

Too little hGH can be caused by a number of different factors.  A genetic mutation in the gene coding for the hormone, a problem with the chemical signal that controls hGH release, or any kind of structural malfunctions in the pituitary or hypothalamus glands can cause a lack of the hormone.  If the hormone is deficient in childhood, a lack of overall growth will result, leading to a condition sometimes referred to as ‘dwarfism’.  If the deficiency begins during adulthood the symptoms often include fatigue, loss of muscle mass, and heart disease.

A synthetic form of the hormone is available today as a treatment for conditions resulting in a lack of the natural version.  Treatment with human growth hormone is also sometimes used for AIDS patients to help them maintain weight in later stages of the disease, in the treatment of fibromyalgia, ulcerative colitis, Crohn’s disease.  A few somewhat controversial uses of the hormone include helping bodybuilders gain muscle, obese people lose weight, and elderly people reverse some of the effects of their age.