Lower circulating IGF-1 levels in fibromyalgia: meta-analysis highlighting potential pathogenic role.

Objectives: To evaluate the relationship between circulating insulin-like growth factor (IGF-1) levels and fibromyalgia (FM).

Methods: Meta-analyses were performed to compare serum/plasma IGF-1 levels in patients with FM and healthy controls and in patients with FM according to subgroups based on region, sample size, data type, publication year, and matched variables (age, sex, and/or BMI).

Results: Twelve studies from eleven reports including 512 patients with FM and 308 controls were selected. IGF-1 levels were not found to be decreased in the FM group (standardised mean differences (SMD) =-0.347, 95% confidence interval [CI]: -0.747 to 0.053, p=0.089. However, sensitivity analysis showed that results of one study significantly affected the pooled SMD (SMD =-0.458, 95% CI: -0.822 to -0.093, p=0.014), indicating that the results of this meta-analysis were unstable. Additionally, the SMD changed to be significant after adjusting for publication bias (SMD =-0.513, 95% CI: -0.924 to -0.102). Stratification according to data type showed a significantly lower IGF-1 level in the FM group with original data (SMD =-0.458, 95% CI: -0.857 to -0.060, p=0.024). Stratification by publication year revealed a significantly lower IGF-1 level in the FM group by recent year (year >2012) (SMD =-0.679, 95% CI: -1.066 to -0.293, p=0.001).

Conclusions: Our meta-analysis demonstrated that IGF-1 levels were significantly lower in patients with FM, suggesting that IGF-1 might play an important role in the pathogenesis of FM.