Postmenopausal osteoporosis is by far the most common cause of age related bone
loss. Growth hormone (GH) is not only important for linear body growth during
childhood, but it is also a major determinant of adult bone mass. GH secretion
diminishes with aging. Therefore, there might be a causal link between the agerelated
decline in GH secretion and bone loss after menopause. So, the present study
was designed to investigate the effect of growth hormone releasing hexapeptide
(GHRP-6), a synthetic GH secretagogue, on bone loss in ovariectomized albino rats
and to compare the results with those of estrogen replacement therapy as a strategy
for treatment in such condition. All rats (except the control rats) were subjected to
bilateral ovariectomy and were divided into four groups (10 rats each): sham
operated control, ovariectomized (OVX), OVX+ estrogen supplemented and
OVX+GHRP-6 treated groups. Rats were administrated their treatments
subcutaneously daily for 6 weeks. In the present study, GHRP-6 was equally powerful
as estrogen in preventing OVX-induced bone loss. Even more, it caused a +ve shift
between bone resorption and bone formation for the benefit of bone formation as
evidenced by the higher serum levels of alkaline phosphatase (a marker of bone
formation) without any significant change in acid phosphatase level (a marker of
bone resorption). In conclusion, GHRP-6 prevents ovariectomy-induced bone loss in
albino rats mainly via preservation of bone tissue and increasing bone formation.
Hence, GHRP-6 could be of value for postmenopausal osteoporotic women who
cannot tolerate estrogens or for whom estrogens are contraindicated.