BGLAP encodes osteocalcin, a multifaceted bone-derived hormone with both structural and endocrine functions. Structurally, osteocalcin is the most abundant non-collagenous protein in bone tissue, synthesized by osteoblasts and incorporated into the bone matrix where it binds hydroxyapatite in a calcium-dependent manner and regulates apatite crystal alignment 1. Its expression is directly regulated by transcription factors Runx2 and Sp7, which are essential for osteoblast differentiation and bone formation 1. As a hormone, uncarboxylated osteocalcin exhibits broad systemic effects. It regulates energy metabolism by promoting pancreatic β-cell proliferation and insulin secretion, while reducing visceral fat accumulation and fasting glucose levels 2. Decarboxylated osteocalcin crosses the blood-brain barrier to promote neuronal survival in the hippocampus and influence monoamine neurotransmitter synthesis 3. Additionally, it acts as a ligand for GPRC6A on testicular Leydig cells to stimulate testosterone production 3. Maternal osteocalcin crosses the placenta to support fetal brain development 3. Genetic variation at the BGLAP locus correlates with bone mineral density in postmenopausal women, suggesting involvement in osteoporosis risk 4. BGLAP expression is suppressed during mesenchymal stem cell senescence through NAP1L2-mediated histone deacetylation, impairing osteogenic differentiation in aging 5. Vitamin D upregulates BGLAP expression in osteoblasts, supporting its role in mineralization 6.