If having kids has made you feel like less of a party animal, men, you now have some science backing you up. A new study following men from their single salad days through the early years of their children’s lives found that fathers had a steeper decline in testosterone levels than men who remained single and childless. Though previous studies had indicated that fathers had lower testosterone, this is the first study to look at men before and after fatherhood, showing that it’s not just that lower-testosterone males are more likely to become dads. (In fact, this study shows the opposite—it’s the hormone-pumped guys who are more likely to settle down with a partner and have kids.)
But testosterone declines naturally with age, and stress is known to contribute to cellular aging. Is the accelerated decline because zero sleep, frayed nerves, and other byproducts of procreating are making men old before their time? That’s a question for next time—this study doesn’t address the decline’s cause.
Image courtesy of edenpictures / flickr
From Ed Yong:
In an Israeli laboratory, Shani Gelstein is harvesting a woman’s tears. The volunteer is watching the end of the boxing film The Champ. As she weeps, she holds a vial under her eyes to capture the fresh drops. This might seem ghoulish, but Gelstein has used the collected tears to understand why people cry during emotional times. She thinks they’re a chemical signal.
Gelstein used several different techniques to show that the smell of a woman’s emotional tears could reduce a man’s sexual arousal. The men never actually saw anyone cry, and they didn’t know about what they were smelling. Even so, their sniffs reduced their testosterone levels and they lowered the activity in parts of their brain involved in sexual desire.
The small study had men smell both women’s tears and saline that had dripped down women’s cheeks, and measured the men’s reactions. The fascinating (if preliminary) results suggest new possible reasons why we cry at emotional times–read the rest of the story at Not Exactly Rocket Science.
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Image: Science / AAAS
It feels good to win. And it feels even better to win at home.
For a new study in the Proceedings of the National Academy of Sciences, Matthew Fuxjager and his colleagues investigated the winner effect, wherein animals (and perhaps humans) build up testosterone in advance of a confrontation, and the fight’s winner maintains that elevated level. By studying male mice fighting one another, Fuxjager was able to see what happens in the brains of winners. Not only did victorious mice experience the “winner effect,” but those who won at home—in their own cages—saw the most activity, and wanted to keep on fighting.
To get these results, Fuxjager’s team essentially created a tournament of mouse fights.
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All it takes for some people to be a little less trusting of their fellow humans is a little more testosterone, according to a new study in the Proceedings of the National Academy of Sciences.
Researchers led by Jack van Honk of the Netherlands used a sample of 24 women in their study. The team showed photos of 150 strangers’ faces to the women and asked them to rate the faces for trustworthiness, using a scale from -100 to +100. The scores women gave after receiving a placebo became their “baseline” score. The women also completed a trustworthiness survey after being given an increase in testosterone instead of placebo (they weren’t told when they received which).
Scientists found that women were not so easily taken in by a stranger’s face after receiving a dose of the hormone…. Women who appeared the most trusting after receiving the “dummy” placebo reduced their scores by an average of 10 points when their testosterone was boosted [Press Association].
Why? The researchers point to the social advantages testosterone can confer:
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A spike in testosterone may not always turn you into a greedy, aggressive, power hungry monster. According to research led by Ernst Fehr, testosterone’s true effect may be to encourage status-seeking behavior, and it can actually make people play more fairly with others.
What’s more, its biological effects on a person may be overruled by that person’s beliefs. In a game-playing experiment set up by Fehr in which some people received a testosterone shot while others got a placebo, those who suspected they had received bona fide testosterone acted more selfishly than those who believed they got the bogus treatment, no matter what they actually received [New Scientist].
Fehr and colleagues used the ‘ultimatum bargaining’ game to test how testosterone would affect behaviour in a group of 121 women. Counter-intuitively, women who were given testosterone bargained more fairly. But the idea that testosterone causes aggression in humans, as it clearly does in rodents, is so firmly ingrained in the human psyche that women who believed they had been given testosterone — whether or not they had — bargained much less fairly [Nature News]. The researchers tested women because they have little variation in their normal testosterone levels. The authors, who published their work in the journal Nature, say their results essentially debunk the popular wisdom that says testosterone causes aggression. Rather, their findings reinforce another idea–hormones are complicated, and testosterone is no exception.
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Men who want to know if they’d make it as day traders on Wall Street just have to look down at the fingers, according to a new study. The longer their ring fingers are in relation to their pointer fingers, the more likely they are to have what it takes to make millions on the trading floor. Previous research has found that the digit ratio reflects how much testosterone an unborn baby was exposed to in the womb. Those exposed to high levels of the hormone are more sensitive as adults to testosterone that creates feelings of confidence and encourages risk-taking, said study author John Coates [Bloomberg].
Coates has previously shown that traders who register the highest levels of testosterone in the morning make the most money through the course of the day, and this new study adds to the earlier work by suggesting that their advantage may have been innate, not learned. Although it may come as no surprise that testosterone could be a big player in the mano-a-mano world of Wall Street, the research offers the best evidence yet of the hormone’s role in determining which would-be Masters of the Universe will thrive. It also supports the growing recognition that biology plays a role in complex human behaviors, and that financial choices in particular are often less rational than economists appreciated [Washington Post].
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Dosing menopausal women with testosterone may be the key to helping those with low libidos get back in the mood, according to a new study. Proctor & Gamble Pharmaceuticals has published the results of a new trial of their testosterone patch, called Intrinsa, and say the results are encouraging for frustrated older women seeking a “Viagra for women.” However, nagging safety concerns are likely to keep the drug off the market in the United States for some time to come (although the drug is already on sale in Europe): During the new study, four of the test subjects using the patch developed breast cancer.
The 52-week study included 814 women with sexual desire disorder, characterized by troublesome low sexual desire or function…. The women were asked to keep sexual encounter diaries, and researchers used other established measures to assess sexual response during the six-month evaluation phase of the study. They found that compared to placebo users, the women who used the 300 microgram patch reported significant improvements in sexual functioning, including desire, arousal, orgasm, and pleasure [WebMD].
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Male-to-female transsexuals are more likely to have a genetic variant that may cause weaker testosterone signals in the brain during early development, according to a new study. Researchers say the finding is another piece of evidence that there is a genetic component to these men’s strong feelings that they’re really women who were born into the wrong body, a theory many experts have long endorsed based on anecdotal evidence. “People who come to our clinic describe how they knew they were different at a very early age, just three or four years old. This is something that people are born with,” Dr [Trudy] Kennedy said [Sydney Morning Herald].
The findings are important, but lead researcher Vincent Harley admits he hasn’t discovered a clear, single cause of transsexualism. While the genetic link was statistically significant, it was weak – 55% of the transsexuals had the [genetic variant], compared with 50% of normal men. Harley agrees that many more genes related to male-to-female transsexualism probably remain to be discovered [New Scientist].
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In a finding that has particular relevance right now, as the American public looks for scapegoats for the current financial crisis, a new study has found that men with higher levels of testosterone are inclined to make riskier financial decisions. Just how much riskier? Those with 33 percent more testosterone than average men invested 10 percent more of their dough. The findings are based on saliva samples from 98 male Harvard students taken before they played an investment game with $250 in real money [Scientific American].
Researchers say they didn’t outright prove that it was Wall Street men’s hormones that got us into this mess, but that the evidence is strongly suggestive. “Although our findings do not address causality, we believe that testosterone may influence how individuals make risky financial decisions,” said researcher Coren Apicella…. A recent study also showed that stock market traders made more money on days when their testosterone levels were highest [LiveScience].
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A study of an experimental prostate cancer drug showed dramatic results that have thrilled researchers: The drug shrank prostate tumors and doubled survival rates in more than 70 percent of patients with an aggressive form of prostate cancer. The test subjects were men whose cancer had not responded to other treatments, and who had a life expectancy of about a year.
Although the study, which was published in the Journal of Clinical Oncology [subscription required], covered only 21 patients, the drug is now being tested in more than 250 men with what appears to be similar results, experts said. “There is a general sense in the prostate cancer community that this agent is extremely promising and is very likely to have an important role in the management of prostate cancer patients,” said Dr. Howard M. Sandler [Los Angeles Times]. Experts say the drug could reach the doctors’ offices by 2011.
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A hormone therapy sometimes called “medical castration” that’s used to treat prostate cancer is of no help to patients in the early stages of the disease, according to a new study. What’s more, the treatment’s side effects far outweigh any potential benefit for most patients [Los Angeles Times].
The treatment, which cuts off the production of male hormones, has been found to be effective in treating aggressive prostate cancer that is spreading through the body; this prompted doctors to begin prescribing the hormone therapy to patients with early stage, localized tumors as well. But the results of this new study are likely to reverse that trend. Hormone therapy’s most obvious side effect is sexual dysfunction. Of greater concern are several recent studies linking [these] therapies to diabetes, heart disease, bone fractures, and reduced muscle mass [WebMD].
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