Objectives: We examined correlates of insulin-like growth factor-I (IGF-I), an indicator of growth hormone levels, to identify factors associated with higher levels of IGF-I in old age.
Design: Nested study of cross-sectional correlates and early-life predictors of IGF-I level.
Setting: A longitudinal cohort study, the Framingham Heart Study.
Participants: A total of 790 men and women (mean age 78.5, range 72-94), who had weight, waist and hip circumferences measured at the time of IGF-I measurement.
Measurements: Association of IGF-I with weight, fat distribution, functional status, nutritional indicators, and past health behaviors was assessed. We also examined IGF-I in relation to body composition derived from dual energy X-ray absorptiometry.
Results: IGF-I levels declined with age in both men and women. However, low IGF-I did not show expected associations with low lean mass and increased body fat. Current functional status and grip strength were not associated with IGF-I Low IGF-I was associated with weight loss in men; the strongest associations were with indicators of poorer nutritional status in both men and women. Levels of IGF-I in old age did not vary by past health behaviors.
Conclusion: Although IGF-I declined with age, these data from the Framingham Heart Study did not show expected cross-sectional associations of weight, body fat, and lean mass. The strongest associations were between IGF-I and nutritional indicators. These results suggest caution may be warranted with regard to use of IGF-I as an indicator of growth hormone.