Amid the fierce debate if humans do synthesize and use pheromones or not, a new research made at Duke University Medical Center in Durham, N.C., and The Rockefeller University in New York City could have detected a gene encoding for one odor receptor (of over 400 smell receptors in humans) believed to be a pheromone perceiver, determining if a particular derivate of testosterone induces changes in the mood, resulting odorless, unpleasantly urine scented, or attractively vanilla flavoring.

391 subjects sniffed 66 scents, the culprit chemical being androstenone (abundant in male sweat and urine). An individual's way of perceiving the pheromone androstenone was found to be significantly connected to an odor receptor named OR7D4; mutations in the gene encoding for the receptor changed the olfactory responses of the people to the smell of androstenone and a related molecule, androstadienone (also typical for man's sweat and urine). "This work represents the first example of a direct link between genetic variability in olfactory receptor genes and differences in the sense of smell," said Yoav Gilad, a professor of human genetics at the University of Chicago, not involved in this study.

The Rockefeller researchers led by Leslie Vosshall, an associate professor of neurogenetics and behavior, asked the subjects to check the scents (varying from spearmint to banana to butanol) in two different concentrations and describe what they smelled.

Duke team led by Hiroaki Matsunami, an assistant professor of molecular genetics and microbiology, made DNA analyses, to see if a person's perception of androstenone scent was connected to variations in the OR7D4 gene, as the receptor was previously discovered to interact with the steroid.

The geneticists encountered two gene variations (alleles). Those who had two "normal" genes (62 %) perceived the androstenone scent as intense, foul odor resembling that of urine. Individuals possessing a "common" variant and its allele, found the smell as varying from imperceptible to powerful, but always weak.

"Only 10 of the study participants (2.5 %) had two copies of the mutated gene. [These] subjects indeed show even lower intensity ratings to androstenone and androstadienone in our study, and even described the smell of the steroids as sweet, like vanilla. The fact that some [of these] subjects could smell androstenone suggests additional odorant receptors are activated by these chemicals.", said Hanyi Zhuang, a graduate student in Matsunami's lab.

"The odor receptor has likely been shaped by evolution, because of the role the scent of androstenone and androstadienone plays in evaluating mates. One aspect of it is whether we can find evidence that odorant receptor variants play any roles in physiological changes caused by exposure of these sex steroid-derived odors. In other words, people who have two copies of functional variants might show more changes in mood or hormonal levels when exposed to androstenone or androstadienone", she added.