| "Men increase their levels"
Testosterone Levels in Men
Men who want to become fathers adjust their testosterone levels to make conception more likely, according to new research.
Katharina Hirschenhauser, an expert in sex hormones, and her team at the Institute of Applied Psychology in Lisbon, Portugal, set out to see if there was any link between men's testosterone levels and their sexual behaviour.
They asked 27 volunteers to measure the testosterone in their saliva every morning for 90 days. Over the same period, the men also recorded their sex lives in intimate detail, documenting the "intensity" of each encounter, whether with their regular partner or not.
All the men had different patterns of testosterone peaks and troughs over the period. But in men trying for a baby, peaks in testosterone levels coincided far more often with periods of intense sexual activity. Hirschenhauser says the finding shows men can subconsciously influence their hormone levels. "Males can be responsive to their partners, but only if they want to be," she says.
Jim Pfaus, an expert in sexual neurobiology at Concordia University in Montreal, says this could overturn a common and uncharitable belief about men. "We tend to think of the little brain being disconnected from the big brain," he says.
Coordinating sexual activity with peaks in testosterone makes sense for men who want to be fathers. Rises in testosterone also trigger a hormonal pathway that increases sperm production, making conception more likely. "In short, you're less likely to shoot blanks," says Pfaus.
There may be more to it than wannabe fathers simply having more sex when their testosterone is high, adds Pfaus. It is well known that women are more receptive to sex around the time of ovulation. Previous studies have also shown that women who live together synchronise their periods - probably through pheromonal cues.
Perhaps, says Pfaus, men who want a baby respond directly to their partner's pheromones and synchronise their testosterone peaks with the mid point of their partner's cycle, when they are most likely to conceive.
Hormones and Behavior (vol 42, p 172)