The median of GDNF levels in CSF was higher in ALS patients (33.1 ± 20.5 pg/ml) compared to CTR (21.2 ± 4.3 pg/ml), but the statistical significance was reached only in serum, where ALS patients showed clearly lower levels of GDNF when compared to CTR (107.3 ± 37.7 pg/ml vs. 198.1 ± 41 pg/ml, respectively). This evidence concerns the gene GDNF and amyotrophic lateral sclerosis.