Researchers from Northwestern University have identified the gene that regulates the male libido, opening the door to new treatments for men who experience a lack of sexual desire or who are excessively horny. Publishing their findings in the journal Endocrinology, the study authors say that the key to male sexual arousal lies in the conversion of testosterone to estrogen in the brain by an enzyme called aromatase.
The gene that codes for aromatase is known as Cyp19a1 and is expressed in both the brain and the testes. Given that castrated animals tend to display no sexual activity, it has long been assumed that aromatase in the gonads drives the male libido, yet the role that this enzyme plays in the brain has never been fully investigated.
Researchers created two lines of genetically modified mice, one of which completely lacked the Cyp19a1 gene and therefore had no aromatase in either the brain or the testes, while the other lacked this gene only in its brain tissue.
When placed in cages with ovulating females, the males with no aromatase made no attempts at mating whatsoever. Meanwhile, those that lacked aromatase only in their brains tried to mount females about half as often as regular male mice would. This finding suggests that the conversion of testosterone to estrogen in the brain does play a role in regulating sexual desire.
Commenting on this observation, study author Serdar Bulun said in a statement that “for the first time, we demonstrated conclusively that the conversion of testosterone to estrogen in the brain is critical to maintain full sexual activity or desire in males. Aromatase drives that.”
The researchers claim that their work could lead to new targeted therapies for men with an unusually low or excessively high sex drive.
Current medications for disorders of sexual arousal inhibit the production of aromatase throughout the body, but have been linked with numerous negative side-effects. By targeting aromatase activity in the brain only, however, the study authors say that these undesirable effects can be eliminated.