Urine Smell May Have 'Manly' Attraction

Is there such a thing as a uniquely male smell that attracts females? Yes, and it’s not for sale at the cologne counter.

In fact, it would probably be a dud in the scent industry. Not many men would want to wear it, especially since it would only beckon ladies of the rodent variety.

The distinctive “male” smell was discovered in urine from male mice. It’s produced by a chemical called MTMT (methylio) methanethiol (search). Female mice don’t make MTMT. Neither do castrated male mice, which lack sex hormones. The compound converts easily into an odoriferous gas. Many compounds in the urine are used to signal reproduction and territorial recognition, say the researchers.

A study of MTMT appears in the Feb. 20 advance online edition of the journal Nature. The report comes from researchers including Lawrence Katz, PhD, of Duke University Medical Center.

The study was done on mice, which use odors as a form of social communication, as do many mammals. Obviously, humans behave differently, but smell still sways us in ways we don’t always realize.

“There are persistent reports about the influence of odorant communications in all sorts of behavior in humans -- mothers recognizing infants, wives recognizing husbands, and of course the influence of perfumes and colognes,” says Katz, in a news release.

Urine Smell: A Magnet for Female Mice

“Female mice strongly prefer to smell male (as opposed to female) urine, and they largely ignore the urine from castrated males,” write the researchers.

Analyzing the urine showed that MTMT was the key ingredient. The researchers then gave female mice a choice of urine from castrated male mice or the same urine with a few drops of synthetic MTMT.

The female mice were much more drawn to the MTMT-laced urine. All but two out of 18 female mice “spent significantly more time” smelling it compared with the plain urine, say the researchers.

The female mice were also more interested in MTMT when it was presented in urine, not water. MTMT might indicate urine’s freshness, say the researchers. “MTMT seems likely to advertise the presence of a male from a distance, either as a signal to other males or to attract females,” they write.

“This strongly suggests that sex-specific volatile chemicals in our bodily secretions could also be detected by similar circuitry,” explains Katz, in the news release.

The findings could also offer insight on perception -- how mice (and maybe humans) piece together lots of information to recognize and understand what’s nearby.

In mice, smell processing may involve many parts of the brain and not just the olfactory area, say the researchers. The study also showed that mice brain cells, in the olfactory region of the brain, became excited while inhaling urine with MTMT.

MTMT isn’t likely to be a love potion for people. Tiny amounts of the chemical are found in shiitake mushrooms, but it has a garlicky smell that’s not very alluring, says Katz, in the news release.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Lin, D. Nature, Feb. 20, 2005, advance online edition. News release, Duke University Medical Center.