PD is multifactorial neurodegenerative disease. It has been hypothesized an occurrence of a hypothalamic-pituitary-adrenal axis (HPA) dysfunction in PD. Furthermore, peripheral measures of cortisol have been shown a relation with worsening or exacerbation in non-motor symptoms in PD.

Serum cortisol levels was measured in 111 subjects (n=75 PD patients; n=36 Healthy controls - HC). The Unified PD Rating Scale (MDS-UPDRS) and Hoehn and Yahr (HY) were used to assess the severity of disease. Fatigue Severity Scale (FSS), 1.13 subitem of MDS-UPDRS-I and Verbal fluency test (FAS) were used to assess fatigue and verbal fluency performance, respectively. To compare groups unpaired t-test was performed. Spearman’s correlation and linear regression were used to relate cortisol and non-motor symptoms.

MDS-UPDRS score was 86.34±3.70 and HY was 2.31±0.10. Serum cortisol levels were significantly higher in PD patients compared to HC (t=2.135; p=0.035). Serum cortisol in PD group showed a significant positive correlation with fatigue in MDS-UPDRS-I (r=0.269; p=0.020) and FSS (r=0.354; p=0.004); Furthermore, it was negatively correlated with phonemic domain of FAS (r=-0.301; p=0.01) but not with semantic domain (r=-0.128; p=0.278). Linear regression showed that cortisol has a predictor effect of 13,1% (r²=0.131, p=0.003) in fatigue and 6,8% in phonemic verbal fluency (r²=0.068, p=0.027).