SCG2 (secretogranin II) is a neuroendocrine protein that functions as both a regulator of secretory granule biogenesis and a source of bioactive peptides with diverse physiological roles. The gene encodes a 616-amino acid protein that undergoes proteolytic cleavage at dibasic residues to generate physiologically active peptides, including secretoneurin 1. SCG2 plays a critical role in ovarian function, where it is induced by luteinizing hormone in granulosa cells across species and promotes ovarian angiogenesis through its cleaved peptide secretoneurin 2. In the nervous system, SCG2 mediates experience-dependent circuit reorganization by coordinating bidirectional plasticity of inhibitory synapses onto hippocampal neurons, affecting gamma rhythms and theta phase coupling 3. The protein also functions in immune regulation, where it binds to LILRB4 on monocytic cells, triggering immunosuppressive signaling through SHP recruitment and STAT3 activation, thereby promoting tumor growth 4. Additionally, SCG2 promotes epithelial-mesenchymal transition and proliferation in nasal epithelial cells through activation of the AKT/GSK-3β/Snail pathway 5. Disease relevance includes roles in endometriosis, osteoarthritis, and choroidal neuropathy associated with pachychoroid phenotypes 678.