Low serum levels of insulin-like growth factor-1 are associated with an increased risk of rheumatoid arthritis: a systematic review and meta-analysis.

Insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) are not only involved in individual growth and metabolism, but they are also associated with inflammation and homeostasis of articular cartilage and bone. Recent studies have identified the involvement of IGF-1 and IGFBP-3 in the development of rheumatoid arthritis (RA). Nevertheless, the results were inconsistent, and the relevant data were not synthetically assessed. Therefore, this review aimed to systematically evaluate the associations of serum IGF-1 and IGFBP-3 levels with the development of RA. Several databases were used to retrieve relevant publications (up to January 2018). Pooled standard mean difference (SMD) and 95% confidence interval (CI) were demonstrated using a forest plot. A total of 27 studies from 19 publications were included. Meta-analysis results showed that RA patients had lower serum IGF-1 levels when compared to controls (SMD = -0.650, 95% CI = -1.184 to -0.115, P = .017). However, there was no significant association between serum IGFBP-3 levels and RA (SMD = 0.590, 95% CI = -1.323 to 2.504, P = .545). Subgroup analyses further showed that serum IGF-1 levels in RA patients are discrepant in terms of race, age, and measurement type (all P < .05). In conclusion, the decreased levels of serum IGF-1 were closely associated with the development of RA. Future longitudinal studies are needed to validate the link between serum IGF-1 levels with RA pathogenesis as well as the effects of IGF-1 on RA treatment.