Regarding the chemotaxis of sperms, new insights have been gained during the last 20 years. Olfactory receptors are expressed on the flagellar midpiece of human spermatogenic cells. One of them, OR1D2, is also expressed in the olfactory epithelium. This receptor has been suggested to play a role in sperm chemotaxis and thus in fertility. As OR1D2 is activated by bourgeonal, the aim of the study was to investigate whether patients with idiopathic infertility would exhibit a decreased olfactory sensitivity toward bourgeonal. Participants were 14 patients with idiopathic infertility and 23 controls (all young fathers). After having ascertained normosmia, odor thresholds and intensity ratings for the pleasant and flowery odors of bourgeonal, helional, and phenylethylalcohol were obtained. As a result, patients had specifically decreased intensity ratings for bourgeonal. It suggests that men with unexplained infertility tend to be less suprathreshold sensitive toward the odor of bourgeonal but not to that of other floral odors. It may be speculated that the decreased olfactory sensitivity relates to a decreased functionality of OR1D2, which in turn may be linked to idiopathic infertility.
Keywords: OR1D2; chemotaxis; olfaction; sensitivity; sperm.