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GHRH and the Anabolic Endocrine Cascade
Growth hormone-releasing hormone (GHRH, also known as growth hormone releasing factor (GRF)) is a peptide hormone produced by the hypothalamus at the base of the brain. GHRH, which is secreted in bursts, particularly during sleep, plays a key role in regulating the body's major anabolic endocrine pathway.

GHRH secreted from the hypothalamus is carried to the anterior pituitary gland where it stimulates the production and release of growth hormone (GH). There are a number of growth hormone isoforms, all of which are secreted in response to GHRH.

Pulses of GH released from the pituitary have numerous growth-enhancing and metabolic effects and also stimulate the secretion of IGF-1 (insulin-like growth factor-1) from the liver. IGF-1 has major direct anabolic effects on a range of tissues and also causes the release of numerous other growth factors.

GH, IGF-1 and other growth factors exert negative feedback effects which control and limit secretion of GH and GHRH. This mechanism is important in preventing excessive production and release of GH.

This interaction of GHRH, GH, IGF-1 and related growth factors is referred to as the GH-IGF-1 axis or the anabolic endocrine cascade.

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Principal pathways of the anabolic endocrine cascade (GH-IGF-1 axis). GHRH is of fundamental importance to the activation and control of the cascade which governs the growth and maintenance of a wide variety of human tissues.