Fig. 2: Forest plot of the included studies evaluating fasting ghrelin levels.

Plasma levels of active and total ghrelin in fasting patients with PD and in the control group were compared using standardized mean differences (SMD) and 95% confidence intervals. Significant reductions in both total (SMD: −0.72, 95% CI: −1.22, −0.22; Z: 2.84; P: 0.005) and active (SMD: −0.42, 95% CI: −0.71, −0.13; Z: 2.82; P: 0.005) ghrelin were observed in patients with PD. High heterogeneity was found for total ghrelin (Tau² = 0.49, Chi² = 82.55, df = 8, P < 0.00001, I² = 90%), while moderate heterogeneity was found for active ghrelin (Tau² = 0.07, Chi² = 13.03, df = 5, P = 0.02, I² = 62%). No significant subgroup differences were found (Chi² = 1.06, df = 1, P = 0.30; I² = 5.3%).