TGFB1 and amyotrophic lateral sclerosis: An earlier study assessing TGF-β1 concentrations in serum and cerebrospinal fluid (CSF) of ALS patients found that TGF-β1 serum levels were significantly higher in terminal clinical status ALS patients than controls, and CSF concentrations of TGF-β1 were significantly positively correlated with the duration of ALS [22].