Serum Insulin-Like Growth Factor-1 (IGF-1) in Parkinson's Disease: A Systematic Review and Meta-Analysis.
Sajjad Mahdavi, Shahryar Rajai Firouzabadi, Ida Mohammadi et al.
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In 30 seconds
This systematic review and random-effects meta-analysis examined observational studies comparing serum IGF-1 in people with Parkinson’s disease (PD) and healthy controls, and studies of associations with PD symptoms. Across 18 studies involving 2,480 participants, serum IGF-1 was higher in the PD group than in controls (MD: 21.3 ng/mL; 95CI: 11.49, 31.12; p < 0.001). A synthesis of five studies found an inverse correlation with motor symptom severity, but evidence certainty was low and individual results were heterogeneous. Associations with non-motor symptoms were inconsistent.
Key findings
- Across 18 studies and 2,480 participants, serum IGF-1 was higher in PD than in controls (MD: 21.3 ng/mL; 95CI: 11.49, 31.12; p < 0.001).
- In five studies of 413 people with PD, IGF-1 correlated inversely with motor symptom severity (r = -0.35; 95% CI: -0.53, -0.08; p < 0.01); certainty was low.
- Non-motor symptom associations were not consistent across the included studies.
Why it matters
The findings suggest serum IGF-1 may differ between people with PD and healthy controls and may relate to motor symptom severity. However, the observational evidence does not establish whether IGF-1 is a useful biomarker or explain the direction of the relationship. The inconsistent non-motor findings and low certainty for motor associations underscore the need for further study.
What to keep in mind
The evidence comes from observational studies, and motor symptom findings were heterogeneous with low certainty. Non-motor associations were inconsistent; the review notes that longitudinal research is needed to assess biomarker utility.