Factors correlated with serum insulin-like growth factor-I levels in health check-up subjects.

Background: Most of circulating IGF-I is derived from the liver and circulating IGF-I levels are decreased in several pathological conditions, such as liver cirrhosis, uncontrolled diabetes, renal failure, and malnutrition. However, it has not fully been elucidated which factors modify IGF-I level in a physiological condition.

Objective: To identify the factors which are associated with circulating IGF-I levels.

Design: Cross-sectional study.

Methods: This study included 428 subjects who undertook health check-up. Subjects diagnosed with non-alcoholic fatty liver disease (NAFLD) by ultrasonography were analyzed separately. Univariate and multivariate regression analyses were conducted to identify the factors associated with circulating IGF-I levels.

Results: Regression analyses revealed that serum albumin levels, total-bilirubin levels, calcium levels, and HOMA-IR were positively correlated with IGF-I levels. Serum transaminase levels and habitual drinking (ethanol intake >20 g/day) were negatively correlated with serum IGF-I levels. Although serum IGF-I standard deviation scores (SDS) in subjects with and without NAFLD were comparable, after adjusting confounding factors clarified by multivariate regression analysis, IGF-I SDS negatively correlated with the presence of NAFLD.

Conclusion: In this study, we demonstrated that serum bilirubin and calcium levels are correlated with serum IGF-I levels. Although further study is necessary, these data suggest a presence of interaction between GH-IGF-I axis and bilirubin and calcium metabolism.