Brain response to putative pheromones
in homosexual men
Ivanka Savic*†‡, Hans Berglund§, and Per Lindstro¨m*
Departments of *Clinical Neuroscience and §Medicine, Karolinska University Hospital,
171 76 Stockholm, Sweden; and †Department of Neuroscience,
Center for Gender-Related Medicine, Karolinska Institute, 171 77 Stockholm, Sweden
Edited by Jan-Åke Gustafsson, Karolinska Institute, Huddinge, Sweden, and approved April 4, 2005 (received for review October 27, 2004)
The testosterone derivative 4,16-androstadien-3-one (AND) and
the estrogen-like steroid estra-1,3,5(10),16-tetraen-3-ol (EST) are
candidate compounds for human pheromones. AND is detected
primarily in male sweat, whereas EST has been found in female
urine. In a previous positron emission tomography study, we found
that smelling AND and EST activated regions covering sexually
dimorphic nuclei of the anterior hypothalamus, and that this
activation was differentiated with respect to sex and compound. In
the present study, the pattern of activation induced by AND and
EST was compared among homosexual men, heterosexual men,
and heterosexual women. In contrast to heterosexual men, and in
congruence with heterosexual women, homosexual men displayed
hypothalamic activation in response to AND. Maximal activation
was observed in the medial preoptic areaanterior hypothalamus,
which, according to animal studies, is highly involved in sexual
behavior. As opposed to putative pheromones, common odors
were processed similarly in all three groups of subjects and engaged
only the olfactory brain (amygdala, piriform, orbitofrontal,
and insular cortex). These findings show that our brain reacts
differently to the two putative pheromones compared with common
odors, and suggest a link between sexual orientation and
hypothalamic neuronal processes.