Growth hormone (GH) is a naturally occurring substance produced by the pituitary gland, a small endocrine gland at the base of the brain. GH plays a broad role in various bodily processes from early development through adulthood. It is important for maintaining overall health and supporting the body’s structural and metabolic functions.
Key Biological Roles
Growth hormone influences bone development, particularly during childhood and adolescence. It promotes the growth of long bones by stimulating cartilage cells in the growth plates, which are specialized areas near the ends of bones. This process increases height until these growth plates fuse, typically occurring in late adolescence.
The hormone also plays a role in the development and maintenance of muscle mass. It promotes protein synthesis within muscle cells, which is the process by which cells build new proteins. This contributes to muscle growth and repair, helping maintain healthy muscle tissue.
Growth hormone impacts the body’s metabolism, influencing how the body handles fats, carbohydrates, and proteins. It promotes the breakdown of fats, a process known as lipolysis, which releases fatty acids for energy use. GH can also influence glucose regulation by decreasing glucose uptake by certain tissues, potentially leading to increased blood glucose levels.
Beyond bone and muscle, GH contributes to the growth and maintenance of internal organs and tissues. It supports the repair and regeneration of cells throughout the body, helping to replace damaged cells and maintain tissue integrity. The effects of growth hormone are mediated by insulin-like growth factor 1 (IGF-1), primarily produced in the liver in response to GH stimulation.
How Growth Hormone is Regulated
The production and release of growth hormone are controlled by a complex system. The pituitary gland serves as the primary site of GH synthesis and secretion. This gland releases GH into the bloodstream in pulsatile bursts, meaning its release is not continuous but occurs in intermittent surges.
The hypothalamus exerts direct control over GH release. It produces Growth Hormone-Releasing Hormone (GHRH), which stimulates the pituitary gland to release GH. The hypothalamus also produces somatostatin, also known as Growth Hormone-Inhibiting Hormone, which suppresses GH secretion.
This regulatory system operates through feedback loops. Increased levels of IGF-1, stimulated by GH, can signal back to both the pituitary gland and the hypothalamus to reduce further GH release. This negative feedback helps maintain appropriate hormone levels. Sleep is a notable stimulant for GH release. Exercise and adequate nutrition can also support healthy GH secretion.
Effects of Imbalances
Maintaining balanced growth hormone levels is important, as both excessive and insufficient amounts can lead to various health conditions. When there is an overproduction of GH, the consequences depend on age. In children, before their growth plates have fused, excessive GH leads to gigantism, characterized by abnormally tall stature and proportionally large body parts.
In adults, after growth plates have closed, excessive GH causes acromegaly. This condition leads to continued growth of bones and tissues, particularly in the hands, feet, and face. Individuals with acromegaly may experience enlarged facial features, hands, and feet, along with complications like joint pain, carpal tunnel syndrome, and an increased risk of heart disease and diabetes. Both gigantism and acromegaly result from a benign tumor on the pituitary gland.
Conversely, insufficient growth hormone levels present distinct health challenges. In children, a deficiency can lead to dwarfism, often referred to as growth hormone deficiency, characterized by stunted growth and short stature. These children may also experience delayed puberty and reduced muscle mass.
Adults can also develop growth hormone deficiency, which may result from pituitary damage, radiation, or other medical conditions. Symptoms in adults can include reduced muscle strength, increased body fat, decreased bone density, and impaired quality of life. Addressing these imbalances through medical intervention is necessary to mitigate their health impacts and improve well-being.
Medical Uses
Synthetic growth hormone, developed through recombinant DNA technology, has several therapeutic applications. It is prescribed to treat specific conditions where the body does not produce enough natural GH or when additional GH is beneficial. A primary use is in children diagnosed with growth hormone deficiency, where it helps promote normal growth and achieve a more typical adult height.
Beyond childhood deficiency, synthetic GH is also used to treat adult growth hormone deficiency, which can arise from various causes, including pituitary tumors or trauma. Treatment in adults aims to improve body composition, increase bone density, and enhance overall quality of life. The hormone is also approved for use in certain genetic conditions that cause short stature, such as Turner syndrome and Prader-Willi syndrome.
Its administration is through daily or weekly injections, and the dosage is determined by a healthcare professional. Use of synthetic growth hormone is regulated due to its powerful effects and potential side effects, which can include joint pain, fluid retention, and an increased risk of diabetes. Therefore, it should only be administered under close medical supervision to ensure safety and effectiveness.