Serum IGF-I and C-reactive protein in healthy black and white young men: The CARDIA male hormone study

objective. Animal and human studies suggest that C-reactive protein (CRP) may be inversely associated with serum insulin-like growth factor-I (IGF-I) concentrations. However, most human studies have not controlled adequately for confounding factors, particularly nutritional intake This population-based study examined whether CRP is inversely associated with IGF-I and IGFBP-3 concentrations Methods. In cross-sectional analysis, multivariable linear regression with adjustment for age, BMI. smoking status. alcohol intake. and nutritional factors was used to relate log CRP the independent variable, to IGF-I and IGFBP-3 in a sample of black (n = 364) and white men (n = 486) separately by race Results. Only black men had positive findings: log CRP was significantly associated with IGF-I (beta= -131 ng/ml, p = 0.02) and the difference in mean IGF-I concentrations between the highest and lowest quartiles of CRP was 26 ng/ml There was a statistically significant interaction between log CRP and smoking status (p = 0.02). the regression coefficient for IGF-I predicted from log CRP was significant ill smokers (beta = 39.8 ng/ml, p = 0 0001), but not in non-smokers. The difference in mean IGF-I concentrations between highest and lowest quartiles of CRP was 100 ng/ml for black smokers. There were no associations for IGFBP-3. Conclusions: In our study, CRP levels are inversely associated with IGF-I concentrations in black male smokers: however, the causal nature of the association is unclear and Should be studied further. (C) 2008 Elsevier Ltd All rights reserved.