What is growth hormone?
Growth hormone is released into the bloodstream from the anterior pituitary gland. The pituitary gland also produces other hormones that have different functions. This acts on many parts of the body to promote growth in children. Once the plates in the bones (epiphyses) have fused hormone does not increase height. 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?
Its release is not continuous; it is released in a number of ‘bursts’ or pulses every three to five hours. This release is controlled by two other hormones that are released from the hypothalamus (a part of the brain) releasing hormone, which stimulates the pituitary to release growth hormone, and somatostatin, which inhibits that release.Its levels are increased by sleep, stress, exercise and low glucose levels in the blood. They also increase around the time of puberty. It release is lowered in pregnancy and if the brain senses high levels of hormone or insulin-like growth factors already in the blood.
What happens if I have too much of it?
In adults, excessive growth hormone for a long period of time produces a condition known as acromegaly, in which patients have swelling of the hands and feet and altered facial features. These patients also have organ enlargement and serious functional disorders such as high blood pressure, diabetes and heart disease. Over 99% of cases are due to benign tumours of the pituitary gland, which produce growth hormone. This condition is more common after middle-age when growth is complete so affected individuals do not get any taller.
Very rarely, increased hormone levels can occur in children before they reach their final height, which can lead to excessive growth of long bones, resulting in the child being abnormally tall. This is commonly known as gigantism (a very large increase in height). Overproduction of this hormone is diagnosed by giving a sugary drink and measuring the hormone level over the next few hours. The sugar should cause over production to reduce. However, this does not happen in acromegaly.
What happens if I have too little of it?
Too little 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, a 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.
It is now clear that contributes to both bone mass and muscle mass reaching the best possible level, as well as reducing fat mass during development to an adult. The specialist is therefore likely to discuss the benefits of continuing this after growth has completed until age 25 to make sure bone and muscle mass reach the best possible level. Additionally, it has been linked to a sensation of wellbeing, specifically energy levels. There is evidence that 30-50% of adults with hormone deficiency feel tired to a level that impairs their wellbeing. These adults may benefit from lifelong treatment with growth hormone.