Biomedical Engineering Reference
In-Depth Information
Hypothalmus
GHRH (+ ve)
GHRIH (-vc)
Pituitary
GH
Liver
Direct effect
on many cells
IGF-I
Many growth
promoting effects
Figure 11.8 Overview of the mechanisms by which GH induces its biological effects and how its secretion
from the pituitary is regulated
indicates it is a member of the haemopoietic receptor superfamily (which includes receptors for
several interleukins, GM-CSF and EPO).
Soluble GH-binding proteins (GHBPs) are also found in the circulation. In humans, these GHBPs
are generated by enzymatic cleavage of the integral membrane receptor, releasing the GH-binding
extracellular domain. The exact physiological role of these binding proteins remains to be elucidated.
In serum, GH binds to two such GHBPs, an action that prolongs the hormone's plasma half-life.
11.4.2 Biological effects of growth hormone
GH primarily displays an anabolic activity. It partially stimulates the growth of bone, muscle and
cartilage cells directly. Binding of GH to its hepatic receptor results in the synthesis and release of
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