SCGN (secretagogin) is a hexa-EF-hand calcium-binding protein that functions as a multifaceted regulator of neuroendocrine and immune processes 1. Structurally, SCGN contains three calcium-binding domains and localizes to synaptic terminals, dendrites, and the nucleus 2. Its primary mechanism involves calcium-dependent interaction with SNAP-25, a SNARE complex component essential for regulated exocytosis and hormone secretion 2. Additionally, SCGN functions as a calcium-dependent molecular chaperone that prevents protein aggregation and responds to cellular stress 1. Disease relevance is substantial across multiple systems. SCGN deficiency causes autism spectrum disorder through disrupted oxytocin signaling and abnormal immune activation 3. Loss-of-function mutations impair intestinal neuroendocrine function, precipitating early-onset ulcerative colitis 4. In pancreatic biology, SCGN regulates insulin secretion and is implicated in diabetes pathogenesis 5. Conversely, in clear cell renal cell carcinoma, SCGN suppression occurs during progression, while restoration enhances macrophage recruitment via NF-κB-mediated chemokine secretion, improving immunotherapy responsiveness 6. High SCGN expression correlates with better ccRCC prognosis 7. Finally, SCGN methylation patterns serve as epigenetic biomarkers for chr6 age estimation in forensic applications 8. These diverse roles position SCGN as a critical regulator of synaptic function, neuroendocrine secretion, immune homeostasis, and proteostasis.