title: Somatomedin-C, physical fitness, and bone density.
abstract: Somatomedin-C (Sm-C) or insulin-like growth factor-I, GH and physical fitness decline with age. Physical fitness and muscle strength are important determinants of bone density, and the age-related decline in bone density may be related in part to a decline in fitness and muscle strength. Also, Sm-C has been shown to stimulate osteoblasts in vitro and may effect skeletal muscle mass. We postulated that the age-related decline in GH and Sm-C levels may be related to an age-related decline in physical fitness and/or muscle strength, and the effect of physical fitness and muscle strength on bone may be mediated by Sm-C. We, therefore, examined the relationship between circulating GH and Sm-C levels and physical fitness, as determined by predicted maximal oxygen uptake (VO2max) in 134 normal women, 34 of whom were postmenopausal. In a subgroup of 62 women overall muscle strength was estimated as the sum of the Z-sores for biceps, quadriceps, and grip strength. Overall muscle strength correlated with GH levels (r = 0.28; P less than 0.02), but not with Sm-C levels. There was a significant positive relationship between plasma Sm-C levels and VO2max in all women (r = 0.47; P less than 0.001) and in the postmenopausal group alone (r = 0.05; P less than 0.01). Although there was a significant negative relationship between Sm-C and age (r = -0.36; P = 0.001), VO2max was a better independent predictor than age (r = 0.47; P = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney.
authors.forename: P J
authors.initials: PJ
authors.lastname: Kelly
authors.forename: J A
authors.initials: JA
authors.lastname: Eisman
authors.forename: M C
authors.initials: MC
authors.lastname: Stuart
authors.forename: N A
authors.initials: NA
authors.lastname: Pocock
authors.forename: P N
authors.initials: PN
authors.lastname: Sambrook
authors.forename: T H
authors.initials: TH
authors.lastname: Gwinn
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D015519:Bone Density; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008875:Middle Aged; D015675:Osteocalcin / Q000032:analysis; D010809:Physical Fitness; D012044:Regression Analysis; D013002:Somatomedins / Q000032:analysis*
chemical_list: D013002:Somatomedins; D015675:Osteocalcin; D007334:Insulin-Like Growth Factor I