Olfactory receptors were found to be expressed also in human sperm giving rise to the hypothesis that they might play a role in fertility and sexual behavior. For instance, bourgeonal was demonstrated to be an agonist of sperm cells olfactory receptor, OR1D2. OR1D2 has been found to be expressed in human olfactory epithelium and to play a critical role in human sperm chemotaxis. Recent preliminary evidence showed that olfaction sensitivity (determined by n-butanol olfactory threshold) and sexual desire were associated in young adult males. It is reasonable to hypothesize that bourgeonal olfactory threshold could be related with human sexual behavior and desire. In 37 healthy young adult male volunteers (age range 20-36 years), the bourgeonal odor threshold and the intensity of sexual desire [the latter using the International Index of Erectile Function (IIEF) scale] were examined. In addition, samples of DNA were collected. Allele and genotype frequency of the OR1D2 single nucleotide polymorphisms (SNPs) were then evaluated in order to study the relationship between sexual desire and OR1D2 SNPs expression. The olfactory threshold was categorized as
