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Ghrelin
What Is Ghrelin?
Ghrelin, discovered as the hormone that stimulates growth hormone release from the pituitary
gland, has been determined, along with several other hormones, to have significant effects on
appetite and energy balance. The main source of ghrelin is the epithelial cells in the stomach.
What Does Ghrelin Do?
Stimulation of secretion of growth hormoneRegulation of energy balance:
In humans (and rodents), ghrelin functions to increase hunger through
its action on the brain. Humans injected with ghrelin experienced sensations of
intense hunger. Unexpectedly (because growth hormone has the OPPOSITE effect),
ghrelin seems to suppress fat utilization in adipose tissue. Ghrelin is
indicated as one of a few hormonal signals that convey to the brain the status of
energy balance in the body.
Ghrelin's other purposes range from stimulating gastric emptying, which occurs about half an hour
after eating, to a variety of positive effects on the cardiovascular system. These positive
effects, such as an increase in cardiac output, may be caused directly by ghrelin or may be the
indirect effect of ghrelin's ability to stimulate secretion of growth hormone.
Blood ghrelin concentration is at its lowest right after eating a meal, but
rises during the fast right before the next meal.
Figure 1 (right), adapted from Cummings, et al. Diabetes 50:1714,
2001, shows this pattern and is based on plasma ghrelin assays in ten people over the
course of a day (indicated by the blue line).
In bypass surgery patients (indicated by the red line),
ghrelin blood concentration remains suppressed. |
Figure 1
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