PCSK1N encodes proSAAS, an endogenous inhibitor of proprotein convertase 1/3 (PC1/3) that plays critical roles in prohormone processing and metabolic regulation. As an endogenous ligand for GPR83, PCSK1N is involved in feeding regulation 1. The gene directly inhibits PC1/3 activity by interfering with its C-terminal cleavage, thereby modulating proinsulin processing 2. PCSK1N expression is transcriptionally regulated by Pax6, which binds the Pcsk1n promoter to suppress its expression; Pax6 mutations lead to elevated PCSK1N, compromising PC1/3 function and glucose metabolism 2. In type 2 diabetes, PCSK1N knockout in human β-like cells associates with altered insulin production 1. PCSK1N also serves as a biomarker in neuroendocrine tumors: it is elevated in silent corticotroph adenomas and correlates with tumor size, functioning as part of the adaptive endoplasmic reticulum stress response 3. In MYCN-amplified neuroblastoma, PCSK1N overexpression associates with poor prognosis and correlates with MYCN expression 4. Additionally, cerebrospinal fluid PCSK1N levels are altered in dementia with Lewy bodies, contributing to a diagnostic biomarker panel 5. In the hypothalamus, Pcsk1n expression decreases during recurrent hypoglycemia-induced impairment of counterregulatory responses 6.