Relationship between growth hormone in vivo bioactivity, the insulin-like growth factor-I system and bone mineral density in young, physically fit men and women

Circulating IGF-I is associated with fitness and health outcomes in a population of 846 young healthy men

“…The results of the current investigation provide additional support for this concept by demonstrating that in a large sample (n= 846) of young (mean age of 24 yr) healthy men, higher IGF-I concentrations were positively associated with a number of health parameters related to body composition, cardiovascular health and aerobic fitness/muscle endurance. Our data provide further experimental evidence reinforcing the concept that IGF-I has utility as a biomarker of health and fitness [3,5,[15][16][17][18]. When subjects were partitioned by quintiles of IGF-I, higher IGF-I concentrations were significantly associated with lower age and adiposity as determined by %BF, waist circumference and BMI, but not fat-free mass.…”

Gemstone spectral imaging for measuring adult bone mineral density

“…Regarding the slight difference in the ages at which the peak BMD of vertebral cancellous bone appeared in males and females, which was also reported in a previous study (25), we hypothesize that it may be associated with the separative statistics of males and females, and the numbers of selected cases. Before 40 years of age, the GSI-determined Ca 2+ -water density of the vertebral cancellous bone in females was significantly higher compared with that in males within the same age period; however, after 50 years of age, this density was significantly reduced in females compared with that in males, and the difference was statistically significant (P<0.01), which is consistent with numerous previous studies (26,27). This trend may be caused by the decline of estrogen in females >50-years-old, resulting in reduced vertebral Ca 2+ content (27).…”

Diet, body composition, and physical fitness influences on IGF-I bioactivity in women

“…For example aerobic fitness level [2], bone mineral density [3], and energy and protein intakes [4] have each been shown to be positively correlated with circulating IGF-I, while age [5], body fat [6], and alcohol intake [7,8] are each reported to have a negative relationship with IGF-I concentrations.…”