Alternative names for growth hormone
Somatotropin; GH; human growth hormone; HGH.
What is growth hormone?
Growth hormone is released into the bloodstream from the anterior pituitary gland. The pituitary gland also produces other hormones which have different functions to growth hormone.
Growth hormone acts on many parts of the body to promote growth in children. In adults, it does not cause growth but it helps to maintain normal body structure and metabolism, including helping to keep blood glucose levels within set levels.
How is growth hormone controlled?
Growth hormone release is not continuous; it is released in a number of ‘bursts’ or pulses every three to five hours. Growth hormone release is caused by another hormone (growth hormone-releasing hormone) which is released from a point higher up in the brain (the hypothalamus) and it causes the pituitary gland to release the growth hormone.
Growth hormone levels are increased by sleep, stress, exercise and low glucose levels in the blood. They also increase around the time of puberty. Growth hormone release is lowered in pregnancy and if the brain senses high levels of growth hormone or insulin-like growth factors already in the blood. This reduction in growth hormone levels is affected by another hormone called somatostatin.
What happens if I have too much growth hormone?
Not surprisingly, too much growth hormone causes too much growth. The condition of too much growth hormone in adults is called acromegaly. Over 99% of cases are due to a benign tumour of the pituitary gland. This condition is more common after middle-age when growth is complete so affected individuals do not get any taller.
Very rarely, increased growth hormone levels can occur in children and results in gigantism (a very large increase in height).
Overproduction of growth hormone is diagnosed by giving a sugary drink and measuring the growth hormone level over the next few hours. The sugar should cause growth hormone production to reduce. However, this does not happen in acromegaly.
What happens if I have too little growth hormone?
Too little growth hormone (deficiency) results in poor growth in children. In adults, it causes a reduced sense of wellbeing, increased fat, increased risk of heart disease and weak heart, muscles and bones. The condition may be present from birth where the cause can be unknown, genetic or due to injury to the pituitary gland during development or at birth.
Growth hormone deficiency may also develop in adults due to brain injury, pituitary tumour or damage to the pituitary gland (for example after brain surgery or radiotherapy for cancer treatment). The main treatment is to replace the growth hormone using injections either once a day or several times a week.
In adults and in children who have reached their final height, growth hormone treatment may not be necessary. However, some people prefer to remain on treatment as it gives them a greater feeling of wellbeing. There are no rules to this and it depends on the patient and doctor responsible. Taking growth hormone when adult will not result in increased height.
Written: March 2011. Review due: March 2013