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How does growth hormone affect body tissues?

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Diagram showing the locations of major human endocrine glands in male and female bodies, including pineal gland, hypothalamus, pituitary gland, parathyroid glands, thyroid gland, thymus, adrenal glands, pancreas, kidneys, testes, and ovaries. — Endocrine system The glands of the human endocrine system.

Growth hormone (GH), a peptide hormone secreted by the pituitary gland, plays a vital role in regulating the growth and metabolism of body tissues.12

Mechanisms of Action

GH affects tissues through two primary pathways:
* Direct Action: GH can act directly on various tissues to influence metabolic processes, such as stimulating protein synthesis and increasing fat breakdown to provide energy for growth. It also influences carbohydrate metabolism, which can raise blood glucose levels.32
* Mediated Action: Much of GH's growth-promoting effect is indirect. It stimulates the liver and other tissues to produce and secrete insulin-like growth factor 1 (IGF-1). IGF-1 then acts on target tissues to stimulate both hypertrophy (increased cell size) and hyperplasia (increased cell number).42

Effects on Tissues

GH is essential for the development of essentially all body tissues, most notably bone. By promoting these cellular changes, GH ensures proper physical development during childhood and puberty. Conversely, abnormal levels of GH can lead to significant tissue disturbances, such as gigantism or acromegaly, characterized by the overgrowth of skeleton, cartilage, and soft tissues.23