Pituitary growth hormone
noun, plural: pituitary growth hormones
A growth hormone (GH) is one of the hormones produced by an endocrine gland. It is a polypeptide that, in essence, promotes a wide range of activities in the body which stimulate growth. Generally, this will involve promoting protein synthesis, while the hormone also promotes the lengthening of bones, which in turn helps to provide support for the future growth of the organism. Growth hormones may be produced by the pituitary gland and by the placenta.
The growth hormone produced by the pituitary gland is called pituitary growth hormone or somatotropin. In humans, the pituitary growth hormone is also referred to as human growth hormone (or simply growth hormone). It is distinct from the pituitary growth hormone produced by bovine animals. Bovine somatotropin differs from human growth hormone in terms of structure. In cows, the bovine somatotropin is involved in the regulation of the amount of milk production.
The human growth hormone (hGH) is a polypeptide comprised of 191 amino acids. It is produced, stored, and secreted by the somatotropic cells of the anterior pituitary. Thus, hHG is also referred to as somatotropic hormone. It is encoded by the GH1 gene located at the growth hormone locus on chromosome 17. Two major pathways where hGH stimulates or acts upon are the MAPK/ERK pathway and the JAK-STAT signaling pathway. In MAPK/ERK pathway, the hGH binds to the specific surface receptor on the target cell, e.g chrondrocyte of cartilage, stimulating the latter directly to multiply by cell division. In JAK-STAT signaling pathway, hGH binds to the receptor on the target cell (e.g. liver cells) and eventually stimulates the target cell to produce insulin-like growth factor 1 (IGF-1). IGF-1, in turn, stimulates systemic body growth, promoting growth on almost every cell in the body (e.g. skeletal muscle cells, chondrocytes, osteoblasts, skin cells, hematopoietic cells, etc.).
In humans, the effects of pituitary growth hormone are as follows:
- increases height in children and adolescents
- increases bone mineralization
- promotes lipolysis
- promotes growth of internal organs (except for the brain)
- promotes gluconeogenesis in liver
- reduces glucose uptake in liver
- stimulates immune system
- promotes deiodination of thyroxin to triiodothyronine (active form of thyroid hormone)
The recombinant form of hGH is called somatropin. It is used to treat patients with hGH deficiency. Deficiency of hGH could result in dwarfism whereas an excess of hGH could lead to gigantism.
- somatotropic hormone
- growth hormone 1 (GH1)