Links for Keyword: Hormones & Behavior

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SAN DIEGO – Researchers at the OHSU Oregon National Primate Research Center (ONPRC) have identified a key gene that impacts the timing of puberty and can shorten the time span for reproduction. The research was led by Sergio Ojeda, Ph.D., head of the Division of Neuroscience and a senior scientist at ONPRC. The work will be presented at the Society for Neuroscience annual meeting on Oct 24, 2004 by Claudio Mastronardi, the lead author of the report. "Using a mouse model, our lab has determined that the absence in the brain's hypothalamus of a gene called TTF-1 causes a delay in the onset of female puberty," explained Ojeda. "This work is of particular interest to those investigating both the delay and early onset of puberty in young women. While there is no definitive information, recently a number of research papers have been published suggesting that young women are reaching puberty at an earlier age. Other research has suggested that if this is the case, it may be linked to the nation's obesity crisis." Prior to the research to be reported at the Society for Neuroscience meeting, Ojeda's group performed studies with rats showing that the TTF-1 gene is expressed in a discrete cellular subset of the hypothalamus during sexual development. Then, using a genome-wide approach, they determined that expression of the TTF-1 gene increases in the hypothalamus of nonhuman primates at the onset of puberty.

Related chapters from BP7e: Chapter 5: Hormones and the Brain; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 6308 - Posted: 06.24.2010

WINSTON-SALEM, N.C. – While soy may be beneficial to women in a variety of ways, research in monkeys suggests that it could have an adverse effect on the behavior of men, according to researchers from Wake Forest University Baptist Medical Center. Reporting in the current issue of the scientific journal Hormones and Behavior, the researchers found that in male monkeys, "long-term consumption of a diet rich in soy isoflavones can have marked influences on patterns of aggression and social behavior." Isoflavones are a naturally occurring plant estrogen in soy protein. "Although considerable attention has been directed at the potentially beneficial effects of isoflavones in reducing the risk of various cancers, osteoporosis, cardiovascular disease and postmenopausal symptoms, less effort has been invested in characterizing neurobehavioral effects," according to the study. People have the concept that soy is only beneficial, said Jay R. Kaplan, Ph.D., professor of comparative medicine and anthropology, one of the investigators. "There is the thought that what is good for some is good for all and more is better."

Related chapters from BP7e: Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 5385 - Posted: 06.24.2010

SAN FRANCISCO – Do you ever wonder how the brain determines its response to emotional stimuli? Researchers have now shown a correlation between secretin, a hormone found in gut and brain tissue, and how the brain responds to affective stimuli. Details and implications of this study will be presented at the American Academy of Neurology 56th Annual Meeting in San Francisco, Calif., April 24 – May 1, 2004. Studies using magnetic resonance imaging (MRI) methods have found that individuals with a range of behavioral disorders including schizophrenia, depression, bipolar illness and autism have abnormal amygdala activation in response to facial emotions and other social stimuli. The amygdala, a part of the limbic brain, has emerged as one of the most critical areas influencing how we respond emotionally. It has also been shown to play an important role in emotional learning and in the attribution of emotional significance to stimuli. These MRI findings point to amygdala dysfunction as a potential neurobiological factor in the development of these disorders. Recent evidence suggests that secretin may modulate the functional response of the amygdala. "We wanted to test the hypothesis that administration of secretin alters amygdala responsiveness to affective stimuli in healthy adult males," notes study author Deborah Yurgelun-Todd, PhD, of McLean Hospital and Harvard Medical School, Belmont, Mass.

Related chapters from BP7e: Chapter 5: Hormones and the Brain; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 11: Emotions, Aggression, and Stress
Link ID: 5367 - Posted: 06.24.2010

Brain's natural painkillers are influenced by women's hormones and genes DENVER – We all know people who can take pain or stress much better than we can, and others who cry out at the merest pinprick. We've heard stories of people who did heroic deeds despite horrible injuries, and stereotypes about women's supposedly sensitivity to pain that don't mesh with their ability to withstand childbirth's pain. But what accounts for all these differences in how individuals feel and respond to pain? And why are some people, especially women, more frequently prone to disorders – like temporomandibular joint pain and fibromyalgia – that cause them to feel crippling pain day and night? Researchers at the University of Michigan believe many answers to these questions lie in the brain -- specifically, how the brain controls our responses to pain.

Related chapters from BP7e: Chapter 8: General Principles of Sensory Processing, Touch, and Pain; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 5: The Sensorimotor System; Chapter 8: Hormones and Sex
Link ID: 3436 - Posted: 06.24.2010

COLLEGE STATION, – Sure Santa Claus asks boys and girls what toys they want, but, why they want them is a better question. The answer may have to do with a biological pre-wiring that influences boys' and girls' preferences based on the early roles of males and females, says a Texas A&M University psychologist. It's commonly believed that boys and girls learn what types of toys they should like based solely on society's expectations, but psychologist Gerianne Alexander's work with vervet monkeys is challenging that notion. Alexander, whose research focuses on sex differences in behavior and the biological factors that influence them, examined the monkeys as they interacted with toys. She and her collaborator, Melissa Hines of the University of London, found that the monkeys' toy preferences were consistent along gender lines with those of human children. The study was published earlier this year in "Evolution and Human Behavior."

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 3154 - Posted: 06.24.2010

PITTSBURGH,– For estrogen to enhance learning and memory, nerve cells in the brain called cholinergic neurons are essential to the process, suggest animal studies performed by researchers from the University of Pittsburgh School of Pharmacy and reported in the November issue of Hormones and Behavior, the official journal of the Society for Behavioral Neuroendocrinology. "Estrogen replacement in postmenopausal women has important effects on mood and cognition. This research was focused on trying to understand what estrogen does in the brain to reduce the effects on brain aging and cognitive decline," stated Robert Gibbs, Pharm.D., associate professor of pharmaceutical sciences at the University of Pittsburgh School of Pharmacy. In the study, rats had their ovaries removed and some of the animals had specific cholinergic neurons destroyed. A few weeks after surgery, most of the animals were put on estrogen replacement therapy (ERT), while some were not.

Related chapters from BP7e: Chapter 18: Attention and Higher Cognition; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 14: Attention and Consciousness; Chapter 8: Hormones and Sex
Link ID: 2938 - Posted: 06.24.2010

SAN FRANCISCO, June 21 – Increased levels of the stress hormone cortisol are clearly elevated in child-bearing-aged women who have stopped menstruating – not only in the bloodstream, but also in the cerebrospinal fluid, a senior researcher at the Magee-Womens Research Institute has found. The study is significant because it shows a definitive link between cortisol levels in circulating blood and those in the fluid that surrounds and bathes the brain and spinal cord. "In fact, cortisol levels in the cerebrospinal fluid are even higher than in the circulating bloodstream," said Sarah Berga, M.D., a professor in the departments of obstetrics, gynecology and reproductive sciences and psychiatry at the University of Pittsburgh School of Medicine and a senior investigator at Magee-Womens Research Institute. "This is really important because cortisol is neurotoxic."

Related chapters from BP7e: Chapter 5: Hormones and the Brain; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 11: Emotions, Aggression, and Stress
Link ID: 2263 - Posted: 06.24.2010

CHAMPAIGN, Ill. — Deciding on hormone-replacement therapy – weighing the far-reaching benefits and risks – can give a woman a headache. Now researchers say estrogen may dictate what problem-solving strategies the brain uses to solve problems. According to a study of rats published in the June issue of Behavioral Neuroscience, activation of different parts of the brain may depend on the presence or absence of estrogen. Rats treated with the hormone learned a place-oriented task faster than rats not getting it, but those not on estrogen were faster completing a response-driven task. These tasks are believed to be controlled by different neural or memory systems. “What we found is that given these analogous tasks that require different cognitive strategies, estrogen biased the rats to use a place, or spatial, strategy,” said Donna L. Korol, a psychology professor at the University of Illinois at Urbana-Champaign. “Those not given estrogen are better using a response, or non-spatial, strategy. This suggests that estrogen isn’t just good for all kinds of memory. Rather, it is very specific in dictating what strategy one takes. Estrogen may enhance some and impair other forms of learning.”

Related chapters from BP7e: Chapter 5: Hormones and the Brain; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 13: Memory, Learning, and Development
Link ID: 2067 - Posted: 06.24.2010

By Erik Vance Big test coming up? Having trouble concentrating? Try a little estrogen. Neuroscientists at the University of California, Berkeley, report in a recent study that hormone fluctuations during a woman’s menstrual cycle may affect the brain as much as do substances such as caffeine, methamphetamines or the popular attention drug Ritalin. Scientists have known for decades that working memory (short-term information processing) is dependent on the chemical dopamine. In fact, drugs like Ritalin mimic dopamine to help people concentrate. Researchers have also had evidence that in rats, estrogen seems to trigger a release of dopamine. The new study from Berkeley, however, is the first to show that cognition is tied to estrogen levels in people—explaining why some women have better or worse cognitive abilities at varying points in their menstrual cycles. The Berkeley team examined 24 healthy women, some of whom had naturally high levels of dopamine and some of whom had low levels, as indicated by genetic testing. As expected, those with the lower levels struggled with complicated working memory tasks, such as repeating a series of five numbers in reverse order. When the test was repeated during ovulation, however, when estrogen levels are highest (usually 10 to 12 days after menstru­ation), these women fared markedly better, improving their performance by about 10 per­cent. Surprisingly, those with naturally high dopamine levels took a nosedive in their ability to do complicated mental tasks at that point in their cycle.

Related chapters from BP7e: Chapter 5: Hormones and the Brain; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 13: Memory, Learning, and Development
Link ID: 13979 - Posted: 06.24.2010

By Andrea Thompson Many pregnant women report being more forgetful as their pregnancy progresses, and new research suggests it could be caused by elevated hormone levels affecting the brain. Previous studies haven't turned up a solid link that could explain maternal memory problems, widely reported on an anecdotal basis. "I think women are interested and sometimes worried about their memory, and whether they're going to get it back if they feel that they've lost some of their cognitive function during pregnancy," said researcher Diane Farrar of the University of Bradford and Bradford Institute for Health Research in England. Farrar and her colleagues set out to test the spatial memory of pregnant women — that's the memory that tells us where we parked the car or set down the keys. The researchers also measured the levels of a set of sex hormones in the pregnant women and had them fill out a questionnaire to judge their mood and level of anxiety. The results for the 23 pregnant women in the study were compared with 24 non-pregnant women. During their second and third trimesters, the pregnant women performed significantly worse than the non-pregnant women on spatial memory tests, the study found. The memory effect still held at three months after birth. © 2010 LiveScience.com.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 17: Learning and Memory
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 13: Memory, Learning, and Development
Link ID: 13907 - Posted: 06.24.2010

By Charles Q. Choi With its winners and losers, politics is a lot like sports. Now biologists have the testosterone—or lack thereof—to prove it. Specifically, they have found that male voters who back a losing candidate experience a drop in the hormone. Immediately before and after the 2008 U.S. presidential election result, neuroscientists from Duke University and the University of Michigan at Ann Arbor collected the saliva of 163 college-age participants to determine the amount of testosterone in their systems. Male voters for winner Barack Obama had stable levels of testosterone, but the hormone rapidly declined in males who cast ballots for losers John McCain and Robert Barr. Female voters showed no significant testosterone changes after victory or defeat of their candidate. Past research has shown that winning and losing in sports matches and other competitions affect testosterone levels in men. The new findings, published online October 21 by PLoS ONE, reveal that politics can influence testosterone in men “just as if they directly engaged head to head in a contest for dominance,” says Kevin LaBar of Duke, the study’s senior researcher. In separate work, anthropologist Coren Apicella of Harvard University and her colleagues obtained similar results with a smaller group, findings they will publish this year. “It’s an exciting time for people who study political behavior, where biological factors have largely been ignored,” she notes. “Political scientists are starting to recognize the role of biology, and more and more research is showing there may be some reciprocal interactions between how elections make one feel and how feelings can affect political behavior.” © 2010 Scientific American,

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress; Chapter 8: Hormones and Sex
Link ID: 13682 - Posted: 06.24.2010

Alison Abbott The popular idea that testosterone always makes people more aggressive has been debunked by researchers. A team based in Switzerland has shown that the hormone can make people behave more fairly in an effort to defend their social status. Ernst Fehr, an experimental economist at the University of Zurich, and his 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. Women, not men, were tested because they have less variable 'baseline' blood testosterone levels. The study is published in Nature1. "It is a folk hypothesis that testosterone causes aggression," says Fehr. "But human society is more complex than this." Fair play Several studies in humans have shown positive correlations between high blood testosterone levels and confrontational behaviour. But it has been hard to determine experimentally whether the aggression is caused by testosterone or is instead a consequence of a challenge to a person's social status. The ultimatum game makes it possible to distinguish between these possibilities. © 2009 Nature Publishing Group

Related chapters from BP7e: Chapter 15: Emotions, Aggression, and Stress; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 11: Emotions, Aggression, and Stress; Chapter 8: Hormones and Sex
Link ID: 13549 - Posted: 06.24.2010

By Rachel Ehrenberg The safe answer to how a lantern shark turns its luminescence on and off is: “Any way it wants.” Now researchers have looked into the belly of the beast and found that three hormones act as on-off switches for these glow-in-the-dark sharks. It is the first discovery of hormones controlling bioluminescence in animals, the scientists report in the Nov. 15 Journal of Experimental Biology. Belgian researchers identified melatonin, prolactin and alpha-MSH, three hormones known to control sharkskin coloration, as key players in setting sharks aglow. In all animals investigated up to this point, luminescence is triggered by nerve cells. Finding a parallel pathway to bioluminescence — one that’s controlled by hormones, not nerves — strongly supports the notion that light-emitting powers have evolved multiple times in animals, comments marine scientist Jim Gelsleichter of the University of North Florida in Jacksonville, who was not involved in the research. access The light-emitting cells in some sharks aren’t connected to prominent nerve cells, and the slow onset of their glow hinted that something other than nerves were involved. Exposing patches of skin from lantern sharks to hormones and to nerve signaling molecules confirmed that hormones turn on the sharks’ bluish glow. Melatonin, which in humans is an important hormone for sleep regulation, induced a slow, long-lasting glow in the skin patches that persisted for several hours, researchers show. © Society for Science & the Public 2000 - 2009

Related chapters from BP7e: Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 13435 - Posted: 06.24.2010

By Lindsey Konkel and Environmental Health News Seeking healthful foods, Americans are eating more soy than ever. But recent research with animals shows that consuming large amounts could have harmful effects on female fertility and reproductive development. Soy is ubiquitous in the American diet. Over a quarter of all infant formula sold is made with it, and the U.S. Food and Drug Administration promotes it in foods to reduce the risk of heart disease. School lunch programs across the country are even adding soy to hamburger patties. Many of soy’s health benefits have been linked to isoflavones—plant compounds that mimic estrogen. But animal studies suggest that eating large amounts of those estrogenic compounds might reduce fertility in women, trigger premature puberty and disrupt development of fetuses and children. Although most studies looking at the hormone-disrupting properties of genistein, the main isoflavone in soy, have been conducted in rodents, many scientists believe the findings may be relevant to humans as well. “We know that too much genistein is not a good thing for a developing mouse; it may not be a good thing for a developing child,” said Retha Newbold, a developmental biologist at the National Institute of Environmental Health Sciences. More definitive answers, she said, may lay ahead in future long-term human studies. © 1996-2009 Scientific American Inc.

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 13: Memory, Learning, and Development
Link ID: 13431 - Posted: 06.24.2010

By Diane Welland The push to prevent skin cancer may have come with unintended consequences—impaired brain function because of a deficiency of vitamin D. The “sunshine vitamin” is synthesized in our skin when we are exposed to direct sunlight, but sunblock impedes this process. And although vitamin D is well known for promoting bone health and regulating vital calcium levels—hence its addition to milk—it does more than that. Scientists have now linked this fat-soluble nutrient’s hormonelike activity to a number of functions throughout the body, including the workings of the brain. “We know there are receptors for vitamin D throughout the central nervous system and in the hippocampus,” said Robert J. Przybelski, a doctor and research scientist at the University of Wisconsin School of Medicine and Public Health. “We also know vitamin D activates and deactivates enzymes in the brain and the cerebrospinal fluid that are involved in neurotransmitter synthesis and nerve growth.” In addition, animal and laboratory studies suggest vitamin D protects neurons and reduces inflammation. Two new European studies looking at vitamin D and cognitive function have taken us one step further. The first study, led by neuroscientist David Llewellyn of the University of Cambridge, assessed vitamin D levels in more than 1,700 men and women from England, aged 65 or older. Subjects were divided into four groups based on vitamin D blood levels: severely deficient, deficient, insufficient (borderline) and optimum, then tested for cognitive function. © 1996-2009 Scientific American Inc

Related chapters from BP7e: Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 8: Hormones and Sex
Link ID: 13425 - Posted: 06.24.2010

Women given testosterone for a month were no more likely than women not receiving the hormone to engage in risky financial decisions, according to researchers in Sweden. The findings could suggest that women are a safer pair of hands on the stock-market trading floor than men — or throw into doubt earlier findings about the effect of the hormone on men. A spate of recent studies have found correlations between testosterone levels and risky behaviour in men, including one that found that male securities traders with more testosterone in their saliva made riskier financial decisions1. But now a team led by Magnus Johannesson, an economist at the Stockholm School of Economics, has found no such effects in a group of 200 post-menopausal women. The women were administered testosterone, oestrogen or a placebo for four weeks and asked to play a series of economic games that measure the player's propensity to take risks, their trust and their willingness to share resources. In the 'dictator game', for example, a player can decide how much of a pot of money they will share with a charity and how much to keep for themselves. The team thought that the testosterone-taking women would behave more like men, giving less to charity and accepting more risk in an investment game. Yet their results, which are published in the Proceedings of the National Academy of Sciences, revealed no meaningful differences between the women who had taken testosterone or oestrogen and the placebo group2. "My assumptions have changed a lot," Johannesson says. © 2009 Nature Publishing Group

Related chapters from BP7e: Chapter 5: Hormones and the Brain; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 11: Emotions, Aggression, and Stress
Link ID: 12727 - Posted: 06.24.2010

By Pat Wingert and Barbara Kantrowitz When Dr. Lauren Streicher, an assistant professor of obstetrics and gynecology at Northwestern University's medical school in Chicago, got a call from "The Oprah Winfrey Show" inviting her to discuss menopausal hormones with actress Suzanne Somers, she figured she'd better read Somers's best-selling books on the subject. As Streicher worked her way through the first chapter, she started underlining every sentence she felt was inaccurate. "But pretty soon, I had to stop," Streicher says, "because I was underlining almost everything."The taping of the show, which aired Jan. 29, proved equally disconcerting. Somers, a self-styled hormone and anti-aging expert whose controversial books promise midlife women that they will feel young and sexy if they take unregulated hormone therapy (HT) in much higher doses and for much longer time periods than most experts recommend, was literally given center stage. She was seated next to Winfrey, the newly proclaimed convert to the so-called bio-identical hormones promoted by the 62-year-old Somers. (Bio-identical generally refers to products that are chemically identical to hormones produced by a woman's body.) While Winfrey, 55, encouraged "every woman" to read Somers's book, the guests with actual medical degrees were relegated to seats in the audience, where they had to sit quietly unless called upon. Interspersed were taped segments of Somers smearing her arms with hormone cream, standing on her head and lining up the 40 dietary supplements she takes with her morning smoothie. The whole setup seemed to give the drugs that Somers uses the same enthusiastic endorsement that turns everything Winfrey promotes into a blockbuster. The resulting spectacle disappointed many doctors who thought Winfrey had higher standards for the quality of medical information she dispersed—or, at least, more of a commitment to balance. Some said they were particularly upset because doctors had complained to Winfrey's production company about what they saw as misinformation disseminated during the show she did on hormone therapy two weeks before that featured Dr. Phil McGraw's wife, Robin. © 2009 Newsweek, Inc.

Related chapters from BP7e: Chapter 5: Hormones and the Brain; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 12547 - Posted: 06.24.2010

By INGFEI CHEN Contrary to popular belief, premenstrual syndrome does not bedevil all women. In the days before their menstrual period begins, an estimated 20 to 40 percent of women experience changes like bloating, headaches and crankiness that are bothersome enough to be called PMS. A far smaller slice of the female sex — just a few percent — suffer severe mood symptoms that would qualify as premenstrual dysphoric disorder, or PMDD. For these women, life is roiled at work, home and in social relationships for a week or so each month as an emotional rollercoaster plunges them into profound sadness or takes them to peaks of frustration or anxiety. But the troubles vanish after menstruation begins. The very existence of this severe form of PMS is, however, an old — and ongoing — flashpoint of controversy. PMDD stirred passionate protests 20 years ago, when the American Psychiatric Association considered adding the diagnostic category to the 1994 edition of its clinical practice bible, the Diagnostic and Statistical Manual of Mental Disorders, or DSM. Women’s health activists argued that the diagnosis pathologized the menstrual cycle and would stigmatize many women by wrongly labeling them mentally ill, and put them in jeopardy of discrimination at the workplace or in child custody battles. Copyright 2009 The New York Times Company

Related chapters from BP7e: Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases; Chapter 15: Emotions, Aggression, and Stress
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 11: Emotions, Aggression, and Stress
Link ID: 12451 - Posted: 06.24.2010

By Janet Raloff On December 18, a National Research Council panel told the Environmental Protection Agency that sufficient data exist to begin assessing the potential health risks posed by phthalates, among the most ubiquitous pollutants on the planet. At the same time, the NRC panel strongly recommended that the agency adopt a “paradigm shift” in the way it assesses the chemicals’ toxicity to humans. Instead of evaluating each phthalate compound individually, EPA should begin assessing risks from likely combos of these and related chemicals — even if each chemical works differently, according to the panel’s new report. Phthalates are a widely used family of plasticizers and solvents. Owing to the chemicals’ presence in plastics, cosmetics, personal care products and even medicines, residues of these chemicals show up in everyone throughout the developed world. For more than a decade, studies in rodents have been demonstrating that exposures to phthalates early in life can perturb — in some cases derail — development of an animal’s reproductive organs (SN: 9/2/00, p. 152). Males are most sensitive, largely because these chemicals act as anti-androgens. That is, the chemicals lower concentrations of testosterone, the primary male sex hormone. Especially concerning: In females, phthalates can cross the placenta and pollute the womb. © Society for Science & the Public 2000 - 2008

Related chapters from BP7e: Chapter 5: Hormones and the Brain; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 12359 - Posted: 06.24.2010

To say that kids are growing up faster than ever these days may be more than just cliché. Recent studies have shown that children are reaching puberty at younger and younger ages, and researchers are starting to see links between this trend and other societal ills such as ubiquitous pollution and sedentary lifestyles. In a 2007 report for the Breast Cancer Fund entitled “The Falling Age of Puberty in U.S. Girls: What We Know, What We Need to Know,” ecologist Sandra Steingraber argues that unfettered access to computers and TVs over the last 30 years has led to an increasingly sedentary lifestyle among kids in the U.S. and beyond. Active kids produce more melatonin, a natural hormone that serves as the body’s internal clock and calendar. This could explain why sedentary kids are likely to go through puberty sooner: Their bodies think their decreased melatonin production is a trigger to move into puberty. “[Melatonin is] an inhibitory signal for puberty,” says Steingraber. “The more melatonin you have, the later you go into puberty.” Of course, sedentary lifestyles are also linked to childhood obesity, a condition that often continues—along with the many health problems that can accompany it—into adulthood. A recent National Health and Nutrition Examination Survey (NHANES) found that, between 2001 and 2004, 17.5 percent of children ages six to 11 were overweight—an effective doubling of obesity rates three decades ago. A study by the non-profit Obesity Society came up with a slightly higher figure—20 percent—with the percentages higher for Hispanic, African-American and Native American children. © 1996-2008 Scientific American Inc.

Related chapters from BP7e: Chapter 5: Hormones and the Brain; Chapter 12: Sex: Evolutionary, Hormonal, and Neural Bases
Related chapters from MM:Chapter 8: Hormones and Sex; Chapter 8: Hormones and Sex
Link ID: 11828 - Posted: 06.24.2010