ANPEP and amyotrophic lateral sclerosis: Circulating APN levels were higher in ALS females (26.51 ± 11.6 μg/ml) and lower in ALS males (9.8 ± 5.2 μg/ml) than the corresponding CTR (Fig. 1a) whereas comparable amounts were retrieved in CSF (Fig. 1b) between ALS males and females (respectively, 10.43 ± 5.2 vs. 13.5 ± 11.1 ng/ml, p = 0.7, ns).