GDF15 and supranuclear palsy, progressive, 1: Serum GDF-15 levels were 1394.67 ± 558.46 pg/mL in patients with PD; 1491.27 ± 620.78 pg/mL in patients with PSP; and 978.42 ± 334.66 pg/mL in patients with MSA (Figure 1).