Serum Free and Total Insulin-Like Growth Factor-I, Insulin-Like Growth Factor Binding Protein-1 and Insulin-Like Growth Factor Binding Protein-3Levels in Healthy Elderly Individuals

Abstract

Background: Little is known about the influence of the free insulin-like growth factor-I/insulin-like growth factor binding protein (IGF-I/IGFBP) system on the quality of health and on disability in the elderly population. Design: In a cross-sectional population based study of 218 healthy elderly subjects (age 55–80 yrs) fasting free and total insulin-like growth factor (IGF-I), insulin-like growth factor binding protein-1 (IGFBP-1) and insulin-like growth factor binding protein-3 (IGFBP-3) levels were measured. Subjective quality of health was assessed by asking all participants whether they judged the quality of their health as better, the same or worse than that of their peers. Disability was determined by the Disability Index of the Stanford Health Questionnaire. Results: Mean serum-free IGF-I levels were significantly lower in the 21 subjects who experienced their health as worse than those of their peers, compared to the 181 subjects who experienced their health as better or the same as their peers 0.069 (SE 0.009) vs. 0.093 nmol/l (SE 0.004) (p = 0.04). Mean IGFBP-1 levels were significantly higher in subjects, who felt less healthy than their peers 1.23 (SE 0.26) vs. 0.73 nmol/l (SE 0.82) (p = 0.01). Free and total IGF-I, IGFBP-1 and IGFBP-3 levels, were not different in subjects with the lowest and the highest Disability Index Score. Conclusion: Low free IGF-I and high IGFBP-1 levels are associated with a decreased self-reported quality of health, but are not related to physical disability in the elderly.