OR1D2 is an olfactory receptor that functions both in traditional olfactory perception and in reproductive physiology through sperm chemotaxis 1. The receptor is activated by bourgeonal, which serves as a potent agonist and chemoattractant for human sperm in vitro 1. OR1D2 is expressed in human sperm flagellar midpiece and olfactory epithelium, mediating sperm migration toward bourgeonal through G protein-coupled signaling pathways 2. Beyond reproductive function, OR1D2 is also expressed in human airway smooth muscle cells where its activation by bourgeonal triggers calcium signaling, increases cell contractility, and induces secretion of inflammatory cytokines IL-8 and GM-CSF 3. Clinical studies demonstrate that men with idiopathic infertility show decreased olfactory sensitivity to bourgeonal and reduced sperm chemotactic responses, suggesting OR1D2 dysfunction may contribute to male fertility issues 12. Additionally, bourgeonal olfactory threshold correlates with sexual desire in young adult males 4. OR1D2 is also ectopically expressed in prostate cancer cells, making it a potential diagnostic target 5. The receptor demonstrates complex ligand interactions that don't follow simple lock-and-key models, responding to various odorants beyond bourgeonal 6.