Growth Hormone Releasing Hormone and Aging

[Nelson Vergel]

GHRH:
There are two published trials of GHRH treatment in normal aging (34, 35). Once daily GHRH injections can stimulate increases in GH and IGF-I at least to the lower part of the young adult normal range (36). In a study of 6 months treatment with daily bedtime subcutaneous injections of GHRH(1–29)NH2, alone or in combination with formal exercise conditioning, IGF-I levels increased by 35% (35). Participants had an increase in lean body mass and decrease in body fat (mainly abdominal visceral fat). However, there was no improvement in strength or aerobic fitness with GHRH injections. The study confirmed the benefits of exercise but showed no effect upon IGF-I levels; thus it appears that GH/GHRH and exercise work through different mechanisms. Subjects receiving GHRH also showed no change in scores on an integrated physical functional performance test of activities of daily living, but there was a significant decline in physical function in the placebo group. This finding, suggesting that GHRH can stabilize if not improve physical function, needs confirmation.
Sleep and cognition were also studied in this GHRH trial, with unexpected results. GHRH failed to improve and may even have impaired deep sleep, despite the rise in IGF-I and pulsatile GH. However, GHRH treatment was associated with improved scores in several domains of fluid (but not crystallized) intelligence – those measures previously found correlated with circulating IGF-I levels (16). This intriguing finding is now being studied more systematically in the Somatotrophics, Memory, and Aging Research Trial, or “SMART”.
In a non-controlled 3 month trial of GHRH(1-44)amide in 10 postmenopausal women, increases in both GH and IGF-I levels as well as decreased visceral fat were demonstrated (34). This study also reported improvements from baseline in selected measures of functional performance including timed walking and stair climbing.
Thus as is the case with GH, studies of treatment of healthy seniors with GHRH have a arrived at a consensus on hormonal and body composition effects but inconsistent functional effects. There is a very encouraging but still unconfirmed positive effect on some domains of fluid intelligence.

Source: http://www.ncbi.nlm.nih.gov/books/NBK279163/?report=printable