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