AGE-DEPENDENT CHANGES IN BODY-COMPOSITION IN POSTMENOPAUSAL JAPANESE WOMEN - RELATIONSHIP TO GROWTH-HORMONE SECRETION AS WELL AS SERUM LEVELS OF INSULIN-LIKE-GROWTH-FACTOR (IGF)-I AND IGF-BINDING PROTEIN-3

The present study was performed to investigate the age-dependent chang es in body composition and the possible role of growth hormone (GH), i nsulin-like growth factor (IGF)-I and IGF-binding protein-3 (IGFBP-3) in these changes in postmenopausal Japanese women. A total of 161 Japa nese women aged 45-88 years (mean 62) were enrolled in the cross-secti onal study. Body composition (bone mineral content (BMC), lean body ma ss (LBM) and fat) was measured by dual-energy X-ray absorptiometry, an d the percentage of BMC, LBM and fat was calculated by dividing each a bsolute value of body composition by total body mass, Urinary GH conce ntration divided by creatinine in nocturnal urine samples collected ju st after waking was used as an index of endogenous GH secretion. Serum levels of IGF-I and IGFBP-3 were measured by RIA. Urinary GH levels a s well as serum levels of IGF-I and IGFBP-3 declined with age, BMC, %B MC and LBM also declined with age, while fat mass and %fat did not obv iously change with age. Urinary GH levels as well as serum levels of I GF-I and IGFBP-3 correlated positively with BMC, even if age was taken into account, On the other hand, urinary GH correlated negatively wit h fat and %fat. In contrast, serum levels of IGF-I and IGFBP-3 correla ted positively with fat and %fat. LBM did not correlate with either ur inary GH or serum IGFBP-3 levels but exhibited a weakly positive corre lation with serum IGF-I level. The present study suggests that the GH- IGF-I-IGFBP-3 axis positively regulates bone mass, and that GH and IGF -I-IGFBP-3 inversely regulate fat mass, i.e. GH negatively and IGF-I-I GFBP-3 positively regulates it.