This seems to be impacting girls more than boys, but then there is more research on the impact these chemicals have on girls/women. We don't know what long-term issues boys may develop as they become men.
This comes from More Intelligent Life.
Boys’ voices are breaking earlier; girls are developing breasts as young as six. But why? Fiona Neill meets the Danish scientists who are on the case ...
From INTELLIGENT LIFE Magazine, Summer 2010
In December 2003 a story appeared in the Copenhagen newspaper MetroXpress. It spoke of crisis at the world-famous Copenhagen Municipal Choir School. For the first time since its founding in 1924, the Copenhagen Royal Chapel Choir was having trouble finding enough 12- and 13-year-old boys to send on its annual American tour.
The trip was the culmination of years of training for these young Danish boys, who had been picked out to attend the school when they were eight. The problem was simple but insurmountable: the boys’ voices were breaking younger. The choir required trebles. But the trebles were turning into tenors and instead of a full tour of the United States they had to make do with a whistle-stop tour to Estonia with an adult choir.
The story might have been forgotten had it not come to the notice of Professor Niels Skakkebaek, then head of the department of growth and reproduction at Copenhagen University Hospital. For Skakkebaek it represented an opportunity. His team of paediatric endocrinologists—specialists in glands and hormones—had noticed an alarming increase in the number of children being referred with symptoms of early puberty. The choir story resonated with what they were seeing.
They had seen a surge in the number of young girls showing signs of breast development, some as young as six. They wanted to know if there was a connection between what they were seeing in clinic and what was happening at the choir school. In 1997 researchers had begun pointing to a dramatic decline in the age of puberty in America. Was the same thing now happening in Europe?
Skakkebaek’s department, founded 20 years ago, now occupies the two top floors on the west side of Copenhagen University Hospital. Compared with the children’s ward just across the hallway, it is an oasis of restraint. Researchers wearing white lab coats wander into the corridor, occasionally opening huge chest freezers in search of test-tube samples. In a meeting room a group of scientists discuss a recent research paper on male sperm count. Just opposite, a child involved in a research project lies on a bed having blood tests.
Skakkebaek, now in his 70s, has handed the reins to Anders Juul, a flamboyant, tousle-haired endocrinologist. “We used to think early puberty was an American problem,” Juul tells me, “to do with American lifestyle, hormone-treated beef, obesity, too much sitting around watching TV and playing on the internet. We felt we should repeat studies that we had done in 1991, which showed no change in the age of puberty, to see if we were now experiencing this phenomenon.”
The last 200 years have seen a big drop in the age of puberty in the West. In the Leipzig choir directed by J.S. Bach in the 1700s, the average age of voice break, a late marker of male puberty, was around 18. Between the mid-19th and mid-20th century, the average age for girls having their first period in America and northern Europe dropped from 17 to under 14.
At first glance it might seem an evolutionary contradiction that as the average age of marriage was rising, the age of sexual maturity was falling. But this trend has its own logic: human beings reproduce when they are healthy. As nutrition and health care improved, the age of puberty dropped. From 1950 onwards the age of puberty plateaued.
In 1950 a British paediatrician, Dr James Tanner, introduced a system for mapping the five stages of puberty in boys and girls. Drawing on two decades of research in a children’s home in Hertfordshire, Tanner concluded that the average age of breast development, often the first sign of puberty among girls, was 11.5 years. Among boys puberty, defined as an increase in testicular volume, began at around 11.2 years. The Tanner scale became a benchmark around the world.
In 1997, however, a group of American researchers published a study of 17,000 girls that showed a sudden lurch in the age of puberty. Its author, Professor Marcia Herman-Giddens, found the average age of puberty among white girls had dropped to 9.7 years. Among Afro-Americans, the trend was even more pronounced: girls were hitting puberty at eight. Some were getting there at six, just a year after starting school. The results were controversial. There were questions over methodology: the girls had attended doctors’ surgeries and were therefore not representative of the wider community; researchers hadn’t examined the girls properly, relying on visual evidence of breast development rather than a physical examination. Many of the girls were obese and might have looked as though they were developing breasts when in fact they were simply fat. But then in 2002 a second study revealed similar results. Breast development seemed to be happening between one and two years earlier than Tanner had indicated.
And if breast development was occurring earlier, girls would inevitably get their period earlier. Herman-Giddens suggested that the Tanner scale should be revised in America.
These findings shocked the endocrinology community and set off a new wave of research. So when Skakkebaek and his team saw the news about the choirboys they contacted the Royal Chapel Choir. To their delight, they were told that the school had kept meticulous records of children’s height and weight, and made weekly voice assessments to record any unintentional falsettos. Parents and children were happy for these to be used in the name of research and the results were published in 2006.
“We discovered that over a ten-year period boys’ voices were breaking around four months earlier,” Juul says, surrounded by precarious stacks of research papers and medical journals in his office. “And that the heavier the boy at eight years old, the earlier the age of voice break.”
Another member of the department, Dr Lise Aksglaede, began investigating the age of breast development among Danish girls. Aksglaede has a calm exterior, and behind it, plenty of tenacity: she managed to persuade the parents and teachers of almost a thousand schoolgirls to sign up to her project. The results, published last May, the first of their kind in western Europe, showed that over 15 years the age of breast development in Denmark had dropped a year, from 10.8 years in 1991 to 9.8 years in 2006. They were also having their first periods, on average, three months earlier.
“It would have been significant if we had simply reported that menarche [the first bleeding] was occurring three months earlier in such a short period of time,” Aksglaede says, “but the fact that breast development was occurring a year early is a remarkable change. Something is going on at a population level, something visible is happening right now. In 15 years’ time, will girls be growing breasts two years earlier? It’s extremely worrying because we don’t know why it’s happening.”
In January, the department published a further study of Danish boys. It showed that the age of puberty had dropped by three and a half months over 15 years, reinforcing the results of the choirboy study. In China a study last year reported the lowest-ever average age for breast development, 9.2 years. Dutch and Italian studies have also echoed what the Danes have discovered among boys.
The term puberty comes from the Latin word puberatum, meaning age of maturity. In the past puberty (the process of sexual maturation) and adolescence (the process of psychological development) occurred in tandem. The decoupling of these processes means that the gulf between physical and psychological maturity has never been greater.
Dr Richard Stanhope, a leading British paediatric endocrinologist who has spent 24 years at Great Ormond Street Hospital for Children, believes this presents dramatic challenges. He feels that children who go into early puberty are prematurely sexualised and too immature to deal with the implications. They are more vulnerable to sexual abuse, inappropriate sexual behaviour, sexually transmitted diseases and teenage pregnancy. “It means that children develop sexually much earlier,” Stanhope says. “They are physically ready for sexual reproduction but mentally completely unready.”
Studies have shown that adolescents who go through puberty earlier are involved in more risk-taking behaviour, such as taking drugs, binge drinking and breaking the law. A premature increase in testosterone can lead to aggression in boys who lack the maturity to control impulses. “We all realise that testosterone is a very difficult hormone to learn to live with,” Stanhope says, tapping a pencil vigorously on his pockmarked table, “and if you get a rise in testosterone outside the normal physiological age, then it’s even more of a problem.”
Research published this year in the Australian and New Zealand Journal of Criminology also found increased aggression in girls who reached puberty early. In Britain the uncomfortable reality that children are becoming sexually mature earlier has been overlooked in the recent debate about the over-sexualisation of children. Instead of simply focusing on cynical manufacturers producing padded bras for seven-year-olds, perhaps we should also consider how to respond to the new reality that some girls are now growing breasts at this age.
Stanhope also points out that for women there may be long-term health problems, because early puberty increases exposure to oestrogen. According to Cancer Research UK, a girl who has her first period a year later than her contemporaries has 5% less risk of developing breast cancer in later life. “There may be an important link with breast and ovarian cancer,” Stanhope says. “The earlier a girl has her period, the longer her exposure to oestrogen and this may well have very important sequelae for oestrogen-dependent tumours. This increases her risk of breast cancer, ovarian cancer and of developing cardiovascular problems.”
Girls who reach puberty early are also more likely to develop type 2 diabetes. A 37-year-long study of 61,000 Norwegian women showed that women who got their first period at ten or 11 had a 10% higher mortality rate than those who got their period four years later.
The long-term risks for men are less proven. Stanhope believes research should focus on whether there is a link between early puberty in boys and prostate cancer. He also points out that although early puberty is becoming more common, it still isn’t the norm, and anything that marks children out from their peer group makes life more difficult.