| Stimulating growth hormone production in healthy older men and women can
return hormone levels to those found in younger adults and reduce body fat, according to
research conducted at the University of Washington. Preliminary results of the study
were presented this weekend in San Diego at the annual meeting of the Endocrine Society.
The study focused on the use of GH-releasing hormone (GHRH), a growth hormone
stimulator, to increase production of growth hormone in 60 healthy men and women over age
65. GHRH is normally produced in the brain by the hypothalamus and stimulates production
of growth hormone by the pituitary.
Known mainly for promoting growth during childhood, growth hormone also has important
actions in adults. It regulates body fat, increases muscle mass and strength and is
believed to influence normal mood and cognition. Growth hormone also stimulates increased
production of insulin-like growth factor-I (IGF-I) in the liver and other tissues. IGF-I
is believed to be a major contributor to the effects of growth hormone.
As we age our growth hormone secretion declines. With this decline comes a negative
alteration in body composition. This results in reduced strength and energy, increased
body fat (especially around the abdomen) and psychological changes. Some studies suggest
that age-associated changes in sleep and cognition may also be related to this decline in
growth hormone.
During this five month blinded study, participants self administered injections of
synthetic GHRH or a placebo each evening. Before and after treatment, subjects' hormone
levels, body composition, physical performance and psychological function were tested.
Overnight measurements assessed sleep quality and changes in growth hormone levels.
Compared to placebo, GHRH boosted the night-time secretion of growth hormone by 35
percent, which led to an increase of 50 percent in blood IGF-I levels in men and 20
percent increase in women.
There was a significant 5% reduction in body fat in both men and women. Even though the
hormone effects occurred in both men and women, there were suggestions that estrogen
replacement in women may partially block some of growth hormone's effects.
The effect of the injections seemed to last only two to three hours and it is
speculated that a longer-acting GHRH preparation might have even stronger effects.
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