PCSK1N and Parkinson disease: Another protein, PCSK1N, also called proSAAS, an inhibitor of prohormone convertase 1 (PC1) activity produced by neuroendocrine cells, has been proven to be a biomarker for many neurological disorders, including Alzheimer’s disease (AD), Pick’s disease, and the Parkinsonism-dementia complex (Shakya et al., 2020; van Steenoven et al., 2020).