Effects of repetitive administration of growth hormone-releasing hormone on growth hormone secretion, insulin-like growth factor I, and bone metabolism in postmenopausal women.
This study sought to determine whether GH response to synthetic GHRH was impaired in 13 postmenopausal (55-71 years) as compared with that in 8 eugonadal women and whether IGF-I and bone metabolism were consequently depressed. Thereafter, the effects of daily iv injections of 80-micrograms GHRH-44 for 8 days were studied in the same postmenopausal group. In addition to significantly higher basal IGF-I and osteocalcin levels (P less than 0.005) in eugonadal as compared with the postmenopausal women, the administration of one GHRH-44 injection resulted in significantly higher 120-min postinjection GH maximum peak and cumulative responses in the former group as well (P less than 0.005). Highly significant correlations were observed between 17 beta-estradiol plasma levels and either GH maximum peak or cumulative responses to GHRH-44 when both groups were pooled together, but not when considered independently. In postmenopausal women, a correlation was found between both age and duration of menopause and GH responses. Repeated GHRH-44 injections in postmenopausal women induced a significant increase in GH response (P less than 0.001) as well as in IGF-I levels from day 4 to 8. No phospho-calcium parameters were modified except for a significant rise in osteocalcin from day 2 to 8. These data indicate an age-related loss of sensitivity of somatotrope cells to GHRH-44 in postmenopausal women, partly corrected by repeated daily GHRH-44 injections. As a consequence of the GHRH-induced increase in GH secretion, IGF-I was also enhanced and may be responsible for a stimulatory effect on bone formation, as shown by the osteocalcin increase, uncoupled from bone resorption.
Franchimont
P
P
Department of Medicine, University of Liège, Belgium.
Urbain-Choffray
D
D
Lambelin
P
P
Fontaine
M A
MA
Frangin
G
G
Reginster
J Y
JY
D000328:Adult; D000368:Aged; D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D004958:Estradiol / Q000097:blood; D005260:Female; D013006:Growth Hormone / Q000008:administration & dosage* / Q000378:metabolism*; D006801:Humans; D007275:Injections, Intravenous; D007334:Insulin-Like Growth Factor I / Q000097:blood*; D008593:Menopause / Q000378:metabolism*; D008875:Middle Aged; D013002:Somatomedins / Q000097:blood*
D013002:Somatomedins; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D002118:Calcium