Chapter 5. Hormones and the Brain
Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.
Roger Dobson It is the chemical that has been described by women as a "cuddle drug". Now scientists have discovered that its effect on men is more rampant and long-lasting than just the desire for a quick hug. Oxytocin, a hormone traditionally used to induce labour, is as sexually arousing to men as Viagra, according to new research. Studies conducted in the US found that a married man who sniffed a nasal spray containing oxytocin twice daily became more affectionate to friends and colleagues and recorded a marked improvement in his sexual performance. According to the actual breakdown of results, the man's libido went from "weak to strong", while arousal went from "difficult to easy". Ego certainly wasn't hurt either: sexual performance, according to feedback from his wife, was classed as "very satisfying". Scientists at the University of California believe the findings provide strong support for the idea that oxytocin improves sexual performance and, unlike Viagra, remains a chemical glue within the brain to cement relationships between people. Just how it works is not clear, but some studies have suggested that oxytocin levels rise naturally during arousal. The hormone is also thought to interact with the dopamine system, which is involved in the rewarding aspects of sexual activity. © independent.co.uk
By Janelle Weaver Birth-control pills are known to affect women’s taste in men, at least in laboratory experiments. Now a study of real-world couples suggests that this pill-related preference change could have long-term consequences for a relationship’s quality and outcome. In the lab, women using oral contraceptives show a weaker preference for masculine men—those with high testosterone levels and the corresponding physical hallmarks—than their non-pill-using counterparts. To investigate this issue in a real-world setting, psychologist S. Craig Roberts of the University of Stirling in Scotland and his collaborators gave online surveys to more than 2,500 women from various countries. According to the results, published online October 12 in the Proceedings of the Royal Society B: Biological Sciences, participants who used hormonal contraceptives while choosing their partner were less attracted to him and less sexually satisfied during their relationship than were individuals who did not use hormonal birth control. Pill users were happier with their mate’s financial support and other nonsexual aspects of the relationship, however, and they were less likely to separate. This relationship stability might be caused by the bias of women on the pill toward low-testosterone men, who tend to be more faithful. Roberts suggests that women who met their mate while taking the pill might want to switch to nonhormonal contraceptives several months before getting married to test whether their feelings for their partner remain the same. © 2012 Scientific American,
By Katherine Harmon Years of surgeries and medications were unable to stop Sultan Kosen’s runaway growth. In 2010 at age 27 and a height of 2.46 meters (eight feet, one inch), he became the world’s tallest living man, according to Guinness World Records. But he wasn’t done growing. Kosen had been diagnosed with a growth disorder at age 10 after doctors in his native Turkey found a tumor on his pituitary gland. The tumor triggered the gland to release too much growth hormone. As a result, he has suffered from both gigantism, a condition in which too much growth hormone is secreted during childhood, and acromegaly, a condition caused by too much growth hormone in adulthood. The tumor was technically benign, but it was lodged near the bottom of his brain, making it difficult to operate on. Thus ensconced, the tumor—along with Kosen’s whole body—continued to grow to dangerous proportions. sultan kosen uva surgery So in May 2010, doctors at the University of Virginia Medical Center put Kosen on new medication to limit growth hormone production. Perhaps more importantly, they were also able to perform gamma-knife radiosurgery on his hard-to-reach tumor. Guided by MRI, the doctors used this super-precise technique, which harnesses high-power gamma rays, to disable the tumor without having to do more dangerous invasive surgery. © 2012 Scientific American
Keyword: Hormones & Behavior
Link ID: 16529 - Posted: 03.17.2012
By Jeanna Bryner Managing editor Give a male garter snake a taste of estrogen and watch out, as the hormone turns these lads into the sexiest thing on the block, attracting dozens of other males eager to mate. The finding, published in the Journal of Experimental Biology, has implications for understanding the environmental impact of compounds that mimic the effect of estrogen, found in some chemicals and pesticides. Estrogen, the researchers found, is key to a female's release of pheromones and thus, reproduction. Here's how it works: For the red-sided garter snake, picking up a mate takes but a second and a flick of the tongue. When a male detects a possible mate nearby, he licks the female with a quick flick of his tongue. Researchers say that the chemical cues exuded by the females, called pheromones, are so strong that it takes but an instant for the male to determine the other snake's species, sex, population, reproduction condition, size and age. In fact, the males are totally dependent on these pheromones for snake reproduction. Every spring, tens of thousands of these garter snakes emerge from their limestone caves north of Manitoba, Canada, for mating. Intense competition ensues, as males swarm (and tongue) female snakes in an effort to be the first to mate with her. The frenzy appears as twisting balls of snakes called mating balls. © 2012 msnbc.com
By ANAHAD O'CONNOR Your daily dose of caffeine may tinker with more than just your energy levels. A new study of women ages 18 to 44 found that drinking coffee and other caffeinated beverages can alter levels of estrogen. But the impact varies by race. In white women, for example, coffee appears to lower estrogen, while in Asian women it has the reverse effect, raising levels of the hormone. The study did not look at older women, but women of child-bearing age who enjoy a daily cuppa have little reason to fret, the researchers said. The effects of caffeine on estrogen are so minimal that in healthy women, it has no impact on ovulation or overall health, at least in the short term. “This is important physiologically because it helps us understand how caffeine is metabolized by different genetic groups,” said Dr. Enrique Schisterman, an author of the study and senior investigator at the National Institutes of Health. “But for women of reproductive age, drinking coffee will not alter their hormonal function in a clinically significant way.” The study, which was published in The American Journal of Clinical Nutrition, analyzed data on more than 250 women who were examined one to three times a week over two menstrual cycles. They provided blood samples along with details about behaviors like exercise, eating and smoking. On average, they consumed about 90 milligrams of caffeine a day, equivalent to roughly one cup of coffee. © 2012 The New York Times Company
By GRETCHEN REYNOLDS A newly discovered hormone produced in response to exercise may be turning people’s white fat brown, a groundbreaking new study suggests, and in the process lessening their susceptibility to obesity, diabetes and other health problems. The study, published on Wednesday in Nature and led by researchers at the Dana-Farber Cancer Institute and Harvard Medical School, provides remarkable new insights into how exercise affects the body at a cellular level. For the study, the researchers studied mouse and human muscle cells. Scientists have believed for some time that muscle cells influence biological processes elsewhere in the body, beyond the muscles themselves. In particular, they have suspected that muscle cells communicate biochemically with body fat. But how muscle cells “talk” to fat, what they tell the fat and what role exercise has in sparking or sustaining that conversation have been mysteries — until, in the new study, scientists closely examined the operations of a substance called PGC1-alpha, which is produced in abundance in muscles during and after exercise. “It seems clear that PGC1a stimulates many of the recognized health benefits of exercise,” said Bruce Spiegelman, the Stanley J. Korsmeyer professor of cell biology and medicine at the Dana-Farber Cancer Institute and Harvard Medical School, who led the study. Mice bred to produce preternaturally large amounts of PGC1a in their muscles are typically resistant to age-related obesity and diabetes, much as people who regularly exercise are. © 2012 The New York Times Company
Posted by Sarah Kliff Wired flags a new study that proves many mothers across the country right: For your own sake, you should call home more often. The research comes from Evolution and Human Behavior. It finds that a phone call to mom provides significant stress relief while instant message conversations won’t quell the nerves. The conversations happened after research subjects took a stressful test. As subjects spoke (or typed) with their mothers, the researchers measured changes in levels of cortisol (generally linked to stress) and oxytocin (a hormone linked to pleasure). When subjects talked on the phone, cortisol levels dropped and oxytocin went up. But IMing with Mom looked the same as having no contact at all: The study author tells Wired, “the results suggest that mom’s voice — its tones and intonations and rhythms, known formally as prosodics — trigger soothing effects, rather than what she specifically says.” To summarize in non-chart form: Call your mother! © 1996-2012 The Washington Post
Victoria Colliver, Chronicle Staff Writer Researchers are getting closer to being able to predict who might be more vulnerable to stress even before they experience trauma. A study of Bay Area and New York police academy recruits by researchers at the San Francisco Veterans Affairs Medical Center, UCSF and New York University is considered one of the first and largest studies to look at biological stress indicators before and after traumatic events. "This study is unique because it looks at people before they've actually been exposed to trauma," said lead author Sabra Inslicht, a psychologist at the San Francisco VA Medical Center and an assistant professor of psychiatry at UCSF. Nearly 300 academy recruits took samples of the waking levels of a stress hormone called cortisol. The results, published in last month's issue of the journal Biological Psychiatry, found that recruits with higher cortisol levels shortly after waking up in the morning were most likely to have stressful reactions to trauma years later as police officers. The new study is part of a larger body of research involving hundreds of recruits from the San Francisco, Oakland, San Jose and New York police departments that has been going on for seven years, said Dr. Charles Marmar, who spent 30 years at UCSF before taking over as chairman of the department of psychiatry at NYU's Langone Medical Center. © 2011 Hearst Communications Inc.
By NATALIE ANGIER VIEWED superficially, the part of youth that the psychologist Jean Piaget called middle childhood looks tame and uneventful, a quiet patch of road on the otherwise hairpin highway to adulthood. Said to begin around 5 or 6, when toddlerhood has ended and even the most protractedly breast-fed children have been weaned, and to end when the teen years commence, middle childhood certainly lacks the physical flamboyance of the epochs fore and aft: no gotcha cuteness of babydom, no secondary sexual billboards of pubescence. Yet as new findings from neuroscience, evolutionary biology, paleontology and anthropology make clear, middle childhood is anything but a bland placeholder. To the contrary, it is a time of great cognitive creativity and ambition, when the brain has pretty much reached its adult size and can focus on threading together its private intranet service — on forging, organizing, amplifying and annotating the tens of billions of synaptic connections that allow brain cells and brain domains to communicate. Subsidizing the deft frenzy of brain maturation is a distinctive endocrinological event called adrenarche (a-DREN-ar-kee), when the adrenal glands that sit like tricornered hats atop the kidneys begin pumping out powerful hormones known to affect the brain, most notably the androgen dihydroepiandrosterone, or DHEA. Researchers have only begun to understand adrenarche in any detail, but they see it as a signature feature of middle childhood every bit as important as the more familiar gonadal reveille that follows a few years later. © 2011 The New York Times Company
By Scicurious Hi. In a few minutes I’d like you to stand up and give a short public speech to a judgmental group of people. The speech will be about the current national and international effects of Marbury v Madison, with particular focus on violations of interstate commerce. You have 15 minutes to prepare and the speech will have to be 15 minutes long. I hope you’ve done your research. Nervous yet? If you are, you’re not alone. Fear of public speaking (glossophobia, or just stage fright) is one of the most common fears in the Western world. But it’s ok. We’re going to have you sit with your loved one, who will be able to give you encouragement as you prepare. Do you feel a little bit better? I bet you do. But do you really, actually feel better? Does your body react to stress differently when you’ve got a loved one with you to help you out? It turns out that it might. At least, if you’ve got a specific kind of oxytocin receptor gene. Oxytocin gets a lot of press. And well it should. Recent findings on oxytocin have shown effects on trust, on generosity, on behaviors in austistic children even. Not to mention all the effects that oxytocin has on parental bonding and on your sex life. While many of these studies have looked at levels of circulating oxytocin, or the effects of giving oxytocin (usually as a nasal spray) on behavior, people have recently started to look at the other side of oxytocin: the oxytocin receptor. © 2011 Scientific American,
By Bella English Jonas and Wyatt Maines were born identical twins, but from the start each had a distinct personality. Jonas was all boy. He loved Spiderman, action figures, pirates, and swords. Wyatt favored pink tutus and beads. At 4, he insisted on a Barbie birthday cake and had a thing for mermaids. On Halloween, Jonas was Buzz Lightyear. Wyatt wanted to be a princess; his mother compromised on a prince costume. Once, when Wyatt appeared in a sequin shirt and his mother’s heels, his father said: “You don’t want to wear that.’’ “Yes, I do,’’ Wyatt replied. “Dad, you might as well face it,’’ Wayne recalls Jonas saying. “You have a son and a daughter.’’ That early declaration marked, as much as any one moment could, the beginning of a journey that few have taken, one the Maineses themselves couldn’t have imagined until it was theirs. The process of remaking a family of identical twin boys into a family with one boy and one girl has been heartbreaking and harrowing and, in the end, inspiring — a lesson in the courage of a child, a child who led them, and in the transformational power of love. Wayne and Kelly Maines have struggled to know whether they are doing the right things for their children, especially for Wyatt, who now goes by the name Nicole. Was he merely expressing a softer side of his personality, or was he really what he kept saying: a girl in a boy’s body? Was he exhibiting early signs that he might be gay? Was it even possible, at such a young age, to determine what exactly was going on? © 2011 The New York Times Company
Prenatal steroids — given to pregnant women at risk for giving birth prematurely — appear to improve survival and limit brain injury among infants born as early as the 23rd week of pregnancy, according to a study by a National Institutes of Health research network. Current guidelines recommend giving prenatal steroids to women at risk of delivering between the 24th and 34th weeks of pregnancy. "These findings provide strong evidence that prenatal steroids can benefit infants born as early as the 23rd week of pregnancy," said study author Rosemary D. Higgins, M.D., of the NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). The study was conducted by researchers participating in the NICHD Neonatal Research Network and led by Waldemar A. Carlo, director of the Division of Neonatology at the University of Alabama at Birmingham. The findings appear in the Dec. 7 Journal of the American Medical Association. When given to pregnant woman at risk for preterm delivery, steroid hormones help the fetus's lungs to mature. For infants born preterm, increased lung development improves the chances for survival and may decrease the risk of brain injury. Infants born in the 22nd through the 25th week of pregnancy — far earlier than the 40 weeks of a full term pregnancy — are the smallest, most frail category of newborns. Many die soon after birth, despite the best attempts to save them, including the most sophisticated newborn intensive care available. Some survive, and reach adulthood relatively unaffected. The rest will experience some degree of lifelong disability, including minor hearing loss, cerebral palsy, and intellectual disability.
By Tim Wall A review of 142 studies on the effects of the herbicide atrazine had bad news for testes. "Essentially, atrazine chemically castrates animals. When you look at a male exposed to atrazine, the testes are missing sperm," Tyrone Hayes of the University of California, Berkeley told Discovery News. The effects of atrazine on male development are consistent across all examined animals, found a study published by a team of 22 researchers from more than 60 nations in the Journal of Steroid Biochemistry and Molecular Biology. Mammals, reptiles, and fish were all affected, but amphibians caught the worst of it. In a study by Hayes, male African clawed frogs turned into females after exposure to atrazine, which kills weeds around the world in everything from corn fields to orchards. "And this is not at extremely high concentrations" said co-author of the review Val Beasley of the University of Illinois in a press release. "These are at concentrations that are found in the environment." Humans aren't spared the effects of atrazine, the world's second most common herbicide after glyphosate, Hayes said. Hayes pointed to studies correlating atrazine exposure to low sperm quality, birth defects, miscarriage, and breast cancer © 2011 Discovery Communications, LLC.
By HARRIET BROWN In patients with depression, anxiety and other psychiatric problems, doctors often find abnormal blood levels of thyroid hormone. Treating the problem, they have found, can lead to improvements in mood, memory and cognition. Now researchers are exploring a somewhat controversial link between minor, or subclinical, thyroid problems and some patients’ psychiatric difficulties. After reviewing the literature on subclinical hypothyroidism and mood, Dr. Russell Joffe, a psychiatrist at the North Shore-Long Island Jewish Health System, and colleagues recently concluded that treating the condition, which affects about 2 percent of Americans, could alleviate some patients’ psychiatric symptoms and might even prevent future cognitive decline. Patients with psychiatric symptoms, Dr. Joffe said, “tell us that given thyroid hormones, they get better.” The thyroid, a bow-tie-shaped gland that wraps around the trachea, produces two hormones: thyroxine, or T4, and triiodothyronine, known as T3. These hormones play a role in a surprising range of physical processes, from regulation of body temperature and heartbeat to cognitive functioning. Any number of things can cause the thyroid to malfunction, including exposure to radiation, too much or too little iodine in the diet, medications like lithium, and autoimmune disease. And the incidence of thyroid disease rises with age. Too much thyroid hormone (hyperthyroidism) speeds the metabolism, causing symptoms like sweating, palpitations, weight loss and anxiety. Too little (hypothyroidism) can cause physical fatigue, weight gain and sluggishness, as well as depression, inability to concentrate and memory problems. © 2011 The New York Times Company
by Catherine de Lange How kind you are could be affected by a change in a single gene. What's more, others can tell if you have the gene even if you don't speak a single word. There are several variations of the gene that codes for the receptor for the hormone oxytocin. Aleksandr Kogan at the University of Toronto, Canada, and colleagues wanted to check whether these variations influence behaviour, since high levels of oxytocin are believed to make people more sociable. Kogan's team asked 116 volunteers to watch 23 silent videos that were 20 seconds long. Each showed a person's response to their partner telling them a story of personal suffering. The volunteers were asked to rate how kind and trustworthy the person in the video appeared to be. People with the so-called GG version of the oxytocin receptor gene were judged to be kinder than those with GA or AA versions. The difference? Those with GG variations used significantly more non-verbal empathetic gestures in their storytelling such as smiling and nodding. Kogan expects that this is what influenced the observers' judgements. Further research will be needed to identify the effect of the different genetic variations on oxytocin levels. Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.111265810 © Copyright Reed Business Information Ltd.
By Tina Hesman Saey Researchers have grown a mouse pituitary gland for the first time from embryonic stem cells. Or rather, the pituitary gland grew itself, after Japanese researchers coaxed embryonic stem cells to form the type of tissues that normally surround the gland. The accomplishment, reported online November 9 in Nature, could be the first step toward replacement pituitary glands for people. Self-made glands growing in lab dishes may also help researchers learn how the organs develop inside the body. “There’s a lot in it to be excited about, whether you’re a developmental biologist or interested in clinical applications,” says Sally Camper, a developmental geneticist at the University of Michigan in Ann Arbor. Camper has tried, and failed, to coax embryonic stem cells to form pituitary glands. “It’s a gorgeous piece of work, and it’s just really, really exciting,” she says. Scientists have persuaded stem cells to form particular types of tissues before, but growing a whole organ in a lab dish has been an elusive goal, says pediatric endocrinologist Mehul Dattani of the University College London Institute of Child Health and Great Ormond Street Hospital for Children in London. What allowed Yoshiki Sasai of the RIKEN Center for Developmental Biology in Kobe, Japan, and colleagues to succeed where others have failed is that the group recreated conditions that exist in the part of the brain where the pituitary normally grows. © Society for Science & the Public 2000 - 2011
By Dina ElBoghdady, A chemical used widely in plastic bottles, metal cans and other consumer products could be linked to behavioral and emotional problems in toddler girls, according to a government-funded study published online Monday in the journal Pediatrics. After tracking 244 Cincinnati-area mothers and their 3-year-olds, the study concluded that mothers with high levels of bisphenol A (BPA) in their urine were more likely to report that their children were hyperactive, aggressive, anxious, depressed and less in control of their emotions than mothers with low levels of the chemical. While several studies have linked BPA to behavioral problems in children, this report is the first to suggest that a young girl’s emotional well-being is linked to her mother’s exposure during pregnancy rather than the child’s exposure after birth. Girls were more sensitive to the chemical in the womb than boys, maybe because BPA mimics the female hormone estrogen, which is thought to play a role in behavioral development. The results add to a growing body of research that suggests exposure to BPA poses health risks in humans. While the federal government has long maintained that low doses of BPA are safe, the Food and Drug Administration and other federal agencies are taking a closer look and investing in more research about the chemical’s health effects. © 1996-2011 The Washington Post
Multiple sclerosis might be connected to a lack of steroids in the brain, Alberta researchers have found. MS attacks the brain and spinal cord, causing inflammation and damage that can lead to paralysis and sometimes blindness. In the September issue of the journal Brain, neurologist Dr. Chris Power of the University of Alberta Hospital in Edmonton and his colleagues describe a new potential avenue for treating MS. There are some drugs related to neurosteroids that are actively in clinical trials, Dr. Chris Power said.There are some drugs related to neurosteroids that are actively in clinical trials, Dr. Chris Power said. CBC The discovery centres on neurosteroids, which help brain cells to talk, grow and repair themselves. The findings open up a brain process "that we might be able to direct so that we can prevent damage and maybe even repair the damaged brain," Power said Wednesday. Brains of people who died with multiple sclerosis showed lower levels of neurosteroids, the researchers found. The team believes that by replacing neurosteroids, it might be possible to alleviate symptoms or even prompt recovery, based on the results of their test tube and mouse modeling studies. "We've actually jumped the queue a little bit because there are some drugs related to neurosteroids that are actively in clinical trials," Power said. "This certainly provides fertile ground." © CBC 2011
by Marianne English Though research has shown that women are more likely than men to remember the emotional details of an event, there may be another dividing factor when it comes to memory: birth control. Scientists know people's hormones shape how their memories form. For instance, our fight-or-flight hormones influence how the brain encodes a specific memory, with traumatic events making more of an impact than everyday activities. A portion of the brain called the amygdala works on the receiving end of these hormones and is thought to play a central role in making and storing new memories. Birth control works by reducing the amount of estrogen and progesterone in a woman's body to limit ovulation, but it's unclear whether these hormones affect how a person recalls an event. In one study, researchers looked at whether women taking oral contraceptives remembered events from an experiment differently than women with normal menstrual cycles not on birth control. Seventy-two female subjects were recruited for the study, half on the pill and half not. Each group watched variations of a slide show story that involved a young boy being hit by a car. Before and throughout the slide show, researchers collected saliva samples to measure alpha-amylase -- a chemical that signifies a drop or rise in the fight-or-flight hormone norepinephrine, which increases a person's heart rate during emergencies or stressful situations. © 2011 Discovery Communications, LLC.
by Elizabeth Norton Humans are probably the only species on Earth who nurture their young for 20 years or more. For men in particular, the intensive demands of parenting can come as such a shock that a built-in biological mechanism has evolved to help cope with the change. A new study shows that becoming a father leads to a sharp decline in testosterone, suggesting that although high levels of the hormone may help men win a mate, testosterone-fueled traits such as aggression and competition are less useful when it comes to raising children. Previous research had shown that among new fathers, testosterone levels were lower than in men of the same age who didn't have children. But no study addressed whether parenthood itself was responsible, or whether men who became committed partners and fathers started out with lower levels of the hormone than did their single, footloose friends. To sort out cause and effect, anthropologists Lee Gettler, Christopher Kuzawa, and colleagues at Northwestern University in Evanston, Illinois, and the University of San Carlos in Cebu City, Philippines, checked testosterone levels in a group of men participating in the ongoing Cebu Longitudinal Health and Nutrition Survey. The survey began with a group of some 3000 women who were pregnant in 1983 and followed the general health, nutrition, medical care, and survival of their children; it has since expanded into an intergenerational study of health, education, and sexual behavior as those children grew up and are now having children of their own. © 2010 American Association for the Advancement of Science.