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Serum insulinlike growth factor 1 as possible marker for risk and early diagnosis of Parkinson disease.

BACKGROUND
The level of serum insulinlike growth factor 1 (IGF-1) is increased in idiopathic Parkinson disease (PD).


OBJECTIVES
To assess whether the (1) IGF-1 level is increased in patients with PD at the time of diagnosis, (2) increased IGF-1 level is related to impaired motor function in healthy individuals, and (3) detection of increased IGF-1 level will help to identify persons at risk for PD.


DESIGN
Cross-sectional cohort study.


MAIN OUTCOME MEASURES
Serum IGF-1 was measured in 15 patients with newly diagnosed untreated PD and 139 healthy elderly individuals. Participants at risk for PD (n = 11) were defined as having altered motor function according to the Unified Parkinson's Disease Rating Scale, Part III (UPDRS-III), and dopaminergic dysfunction as indicated by sonographically determined substantia nigra hyperechogenicity.


RESULTS
The IGF-1 level was higher in patients with PD compared with healthy participants (P = .004) and inversely correlated with the UPDRS-III score (ρ = -0.77). The IGF-1 level was not related to motor function in the healthy group. However, there was no significant difference between the IGF-1 level in the at-risk subgroup vs the PD patients (corrected P = .15), and the IGF-1 level was positively correlated with the UPDRS-III score (ρ = 0.80).


CONCLUSION
Serum IGF-1 monitoring may be valuable in the diagnosis of PD and for the identification of individuals with a putatively increased risk for PD.