Puberty Earlier in Boys, Study Finds

A study, published in the Oct 20th, 2012 issue of Pediatrics, found that boys are also beginning puberty earlier than in previous decades.

For an overview of the results, see the following links:

CBS News report

WSJ article

University of Vermont press release 

For details about the study methods and results:

Pediatrics article 

The authors acknowledge that their results should not be interpreted as being statistically representative of boys in the entire U.S. population.  Still, their findings suggest that boys are experiencing a drop in the starting age of puberty, similar to girls.

Some quotes from the Pediatrics article:

pg 1065: "In conclusion, our data suggest that US boys are beginning genital and pubic hair growth earlier than several decades ago in concordance with recent reports on girls. These data are consistent with recent trends from other countries, such as Denmark, Sweden, Great Britain, Italy, and China." 

pg 1065: "Current environmental factors, including exposure to chemicals, changes  in diet, less physical activity, and other modern lifestyle changes and exposures may be related to this apparent rapid decrease in the age of onset of secondary sexual characteristics and may not reflect healthy conditions." 

An interesting contrast in theories about what's causing the drop for boys vs. girls is that obese boys seemed to have later puberty, whereas for girls it is thought to be a risk factor for earlier puberty. Other considerations, such as environmental factors, are similar for boys and girls.

Note that this study addresses earlier puberty in boys, but is not about central precocious puberty, strictly defined.

For related posts, see:

Potential causes

Trends in age of onset of puberty

Strength and weakness of study designs

Central Precocious Puberty, strictly defined

New study on sleep, looking for kids with early puberty

Dr. Natalie Shaw, a Pediatric Endrocrinologist in Boston, is about to start a new research study looking at sleep architecture (i.e., percent of sleeping spent in deep sleep vs. in REM sleep) in children with precocious puberty.  A number of investigators have shown that there is a dramatic decline in slow-wave (deep) sleep that occurs across adolescence and that the decline occurs earlier in girls than in boys (as does puberty), suggesting that sex steroids may be responsible.  To answer this question, Dr. Shaw will enroll kids with CPP in a study which involves two investigations, one at the time of diagnosis, and a second after at least 6 months of treatment for the CPP.  She will then compare their sleep patterns to similar kids who do not have CPP and do a comparison (pre/post treatment).  Dr. Shaw is very interested to see if exposure to sex steroids affect sleep and if so, if the effects are reversible.  If they are not, she would look into what this means for the children's health.

Deep sleep is known to be important in terms of refreshing a child and preparing them for learning the next day.  (For a not-too-technical discussion, click here.)

If you are interested in enrolling your child, or know anyone else who might be interested in doing so, please pass on the information.  Here is the official notice:

The Reproductive Endocrine Unit at the Massachusetts General Hospital seeks healthy girls (4-8 years old) and boys (4-9 years old) who have started puberty (known as precocious puberty), who have not yet begun treatment and who do not have a sleep disorder.  The purpose of the study is to determine the effect of reproductive hormones like estrogen and testosterone on sleep.

This study involves a screening visit (1 hour) and 1-2 overnight stays at the hospital (from approximately 5pm to 9am) for a sleep study and blood sample(s).  The study will take about 6 months to complete. Payment for participation is up to $250.

Call Natalie at 617-726-1895 or email nshaw@partners.org<mailto:nshaw@partners.org> for more information.


Thank you!

Article on Puberty Before Age 10, Today's New York Times

Hi, Everyone.  A big article on signs of puberty at younger ages came out in today's New York Times.  Part of the discussion in it is about what defines "normal puberty".  Some in the medical community feel that earlier breast development without the activation of the brain found in central precocious puberty (CPP) should not be considered abnormal.  In an earlier post, I made my own opinion about that approach clear. 


The possible causes of early development that are discussed in the NYT piece include many that we have already mentioned in this blog, such as: obesity, certain environmental chemicals, and family factors.


I don't think that I am allowed to attach the full text, but I have included excerpts below. The full article can be found on the NYT website here.  

March 30, 2012

Puberty Before Age 10: A New ‘Normal’?

By ELIZABETH WEIL

<>

So why are so many girls with no medical disorder growing breasts early? Doctors don’t know exactly why, but they have identified several contributing factors.
<>
... animal studies show that the exposure to some environmental chemicals can cause bodies to mature early. Of particular concern are endocrine-disrupters, like “xeno-estrogens” or estrogen mimics. These compounds behave like steroid hormones and can alter puberty timing.  
<>

One concern, among parents and researchers, is the effect of simultaneous exposures to many estrogen-mimics, including the compound BPA, which is ubiquitous. Ninety-three percent of Americans have traces of BPA in their bodies. BPA was first made in 1891 and used as a synthetic estrogen in the 1930s. In the 1950s commercial manufacturers started putting BPA in hard plastics. Since then BPA has been found in many common products, including dental sealants and cash-register receipts. More than a million pounds of the substance are released into the environment each year.

<>

 Adding to the anxiety is the fact that we know so little about how early puberty works. A few researchers, including Robert Lustig, of Benioff Children’s Hospital, are beginning to wonder if many of those girls with early breast growth are in puberty at all. Lustig is a man prone to big, inflammatory ideas. (He believes that sugar is a poison, as he has argued in this magazine.) To make the case that some girls with early breast growth may not be in puberty, he starts with basic science. True puberty starts in the brain, he explains, with the production of gonadotropin-releasing hormone, or GnRH. “There is no puberty without GnRH,” Lustig told me. GnRH is like the ball that rolls down the ramp that knocks over the book that flips the stereo switch. Specifically, GnRH trips the pituitary, which signals the ovaries. The ovaries then produce estrogen, and the estrogen causes the breasts to grow. But as Lustig points out, the estrogen that is causing that growth in young girls may have a different origin. It may come from the girls’ fat tissue (postmenopausal women produce estrogen in their fat tissue) or from an environmental source. “And if that estrogen didn’t start with GnRH, it’s not puberty, end of story,” Lustig says. “Breast development doesn’t automatically mean early puberty. It might, but it doesn’t have to.” Don’t even get him started on the relationship between pubic-hair growth and puberty. “Any paper linking pubic hair with early puberty is garbage. Gar-bage. Pubic hair just means androgens, or male hormones. The first sign of puberty in girls is estrogen. Androgen is not even on the menu.”

Frank Biro, lead author of the August 2010 Pediatrics paper and director of adolescent medicine at Cincinnati Children’s Hospital, began having similar suspicions last spring after he flew to Denmark to give a lecture. Following his talk, Biro looked over the published data on puberty of his colleague Anders Juul. In Juul’s study, some of the girls with early breast development had unexpectedly low levels of estradiol, the predominant form of estrogen in women’s bodies from the onset of puberty through menopause. Biro had seen a pattern like this in his data, suggesting to him that the early breast growth might be coming from nonovarian estrogens. That is to say, the headwaters for the pubertal changes might not be in the girls’ brains. He is now running models on his own data to see if he can determine where the nonovarian estrogens are coming from.

<>

Elizabeth Weil is a contributing writer for the magazine and the author of a new memoir about marriage, “No Cheating, No Dying.”

Lavender Oil & Tea Tree Oil

I first became interested in the link between lavender and tea tree oil and signs of early puberty after reading an article in the New England Journal of Medicine (NEJM) related to the topic.  

The article I found, Prepubertal Gynecomastia Linked to Lavender and Tea Tree Oils, presents case studies of three prepubertal boys who developed enlarged breasts (gynecomastia). The boys' doctor, Dr. Clifford Bloch, discovered that they had all used lotions, creams, shampoos, styling products or soap with lavender or tea tree oil in them.  Once these products were stopped, the enlarged breasts went away.

In the NEJM article, the authors also present methods and results from in vitro studies they conducted, which confirmed "that lavender oil and tea tree oil possess weak estrogenic and anti-androgenic activities that may contribute to an imbalance in estrogen and androgen pathway signaling." The in vitro studies suggest that lavender oil and and tea tree oil, may not change the level of hormones in the body, but may interfere with their activity in the body.  The authors also wrote that they observed that the amount of exposure to oils seems to be important, i.e. there may be a threshold, below which there is no reaction, but above which, there is.

This made my head spin as I thought of all the products, which contain these oils. Lavender in particular seems to be in everything for kids, e.g., lotions, soaps, even in pure extract, given its purported soothing effect and pleasing smell. 

Here are some additional points for consideration:

1. I cannot comment on the scientific methods used in the in vitro studies. The findings about the boys, however, are based on 3 case reports.  As I discussed in an earlier post, case reports have the lowest strength of evidence, as they are descriptive (rather than based on statistical analysis) and are based on too few patients to be able to draw any real conclusions.

2. Still, even if the study findings are not conclusive and do not provide strong evidence, it can't hurt to be cautious. The NEJM article authors write:

"Until epidemiologic studies are performed to determine the prevalence of gynecomastia associated with exposure to lavender oil and tea tree oil, we suggest that the medical community should be aware of the possibility of endocrine disruption and should caution patients about repeated exposure to any products containing these oils."

3. The NEJM article was reported based on three boys in one doctor's clinical practice. As far as I know, no larger epidemiological studies have been done for boys, nor have any studies been done to determine whether these oils have similar effects in girls.

4. Even without those studies, however, we know that lavender & tea tree oil probably cannot explain why central precocious puberty (CPP) happens in some girls. The reason I feel confident putting this point so strongly is because central precocious puberty is triggered by the brain and we know that the level of hormones in these girls is affected, which differs from the tea tree oil and lavender oil responses.  (An earlier post, found here, explains how CPP happens.)

Therefore, my own conclusions about lavender and tea tree oils are that it probably cannot hurt to remove products with these from your homes if you have children -- , but I doubt that they will ever be found to be big contributors in the CPP mystery.  Again, what we really need, is a well-designed large-scale study to give us better answers.

Obesity

The trend of rising childhood obesity seems to be the most commonly mentioned potential factor contributing to early puberty in girls.  What might be the connection?

Here is a link to a WebMD article on the topic:

Our fat cells make [the hormone,] leptin. The more fat we have, the more leptin in our systems. Leptin seems to play a key role in regulating appetite, body type, and reproduction.  Leptin doesn't trigger puberty on its own. But there's evidence that for puberty to start, a child has to have enough leptin in her system, Kaplowitz [Paul Kaplowitz, MD, PhD, Chief of the Division of Endocrinology at Children's National Medical Center] says. Girls who have high leptin levels -- because they are overweight -- could be more prone to early puberty.

For those of you who are interested in more scientific details, there are several other pathways for how the increased prevalence of overweight and obesity could trigger early pubertal development.  In their article the authors, CM Solorzano and CR McCartney, discuss some of those.

The primary article referenced to support the obesity and early puberty link seems to be one published in 1997 by ME Herman-Giddens et al.  In a large cross-sectional study [side note: see my earlier post about study designs; cross-sectional is not the best, but a large sample is good[, they found that obesity as measured by Body Mass Index, BMI, was significantly associated with early puberty, although the association was less strong in African-American girls than in white girls.  What this means is that girls who are obese appear to be more likely than girls who are not obese to experience early puberty.  However, please keep in mind that showing an association does not equal proving a causal link between the two.

Part of my discomfort with what sometimes seems like a default focus on the obesity-early puberty connection in the literature and general media is that I know girls who have never been overweight or obese who have been diagnosed with central precocious puberty.  If obesity is a contributing factor, it must not be the only one.

All Studies Are Not Created Equal

Before discussing specific studies related to precocious puberty, it is important to understand that not all studies are created equal.

Often people see results from a study reported in the media and they conclude, "Research has shown ..." without any assessment of the design, strengths and weaknesses of that particular analysis.

Conclusions drawn from a well-designed study have more credibility than a poorly designed one --, but yet often the media don't give any indication of the quality of the studies on which they report. This can be a serious disservice to the public who often take what they read at face value and make health-related decisions based on that.

One aspect of the public health field of epidemiology is the study of risk factors, things that increase the chances of something happening, such as disease. For example, smoking is a risk factor for lung cancer. There are numerous study designs to test the relationship between risk factors and disease. The following observational study types are listed according to the hierarchy from least dependable strength of evidence to most dependable. 

Least Dependable: Case Report
A case report describes the symptoms, signs, diagnosis, treatment, and follow-up of an individual patient with PP (for example). There may be many reasons for that patient's experience. Thus, one case study does not give analytic evidence regarding what is a risk factor for a PP within the broader population.

Case Series
A case series is a descriptive report of a group of patients. Similar to the case report, this is descriptive rather than analytical by nature and is not rigorous, e.g., does not report on enough patients, to be able to scientifically identify risk factors for a disease.

Ecologic Studies
Ecologic studies base their results on data at the population-level (e.g. average childhood obesity rates within the U.S.) rather than individual-level data (presence of obesity in individual girls). The problem with this is that conclusions that are true for averages may not help us understand what is true for the individual. For example, it seems that many girls who develop PP are not in fact obese, so what led to PP for them?

Cross-Sectional Study

Cross-sectional studies look at potential risk factors and outcomes, using data collected just at one point in time. With this approach, there is the question of which comes first, the risk factor or the PP. All you can see is that both are found at a particular point in time.

Case-Control Study

Case-control studies identify cases, people who have the outcome of interest (e.g., girls who have precocious puberty) and controls (girls who have not developed precocious puberty) and looks backwards in time using medical records and other collected data using tools like patient surveys to test which factors or characteristics have a higher association with PP.

This is an improvement from cross-sectional studies, because at least you can look for risk factors that happened before PP was diagnosed.

Most Dependable: Cohort Study

Cohort studies - also called panel studies, use data collected on a group of people over time to determine the effect of different type of risk factors on developing the outcome of interest. To test the associations between risk factors and PP, this would be the ideal study design, i.e. a large sample of girls chosen to participate from the time they are born going forward, looking to see who develops PP and who does not.

Ultimately, to prove causality, an experimental study, rather than an observational ones, gives the best evidence. The gold standard of experimental studies is the randomized controlled trial (RCT), during which one group is exposed in a highly controlled way to a particular exposure and the other group is not. However ethical considerations often make conducting such studies on humans (particularly children) a non-option. Researchers are therefore left to make conclusions based on observational studies or based on experimental studies on animals -- a practice that has its own ethical and methodological limitations.

As I look at specific studies about precocious puberty, I will address some of these study design points, such as:

1. The type of study -- and how much we should rely on its conclusions, based on its design

2. How many people were studied, i.e., the sample size

3. Did the study include only those with precocious puberty (cases), or were those who did not have precocious puberty (controls) also included for scientific comparison?
4. Do the conclusions made in the study match the evidence, taking into account these factors as well as other potential biases in the study?

I would love to see a long-term cohort study that collects data about children beginning with their mother's pregnancies with them and including information related to all of the potential risk factors for precocious puberty (genetics, environmental exposures, nutrition, family environment, etc).  As far as I know this study does not yet exist.   

Media coverage of rise of precocious puberty in 2nd graders

Growing up too soon? Puberty strikes 7-year-old girls
Study in 3 major cities finds precocious puberty rising among 2nd graders

By Linda Carroll

msnbc.com contributor

updated 8/9/2010 7:41:13 PM

The changes in Kiera’s body scared her parents. Though the 8-year-old seemed her usual chipper self, she’d started to develop headaches and acne. More alarming to her mom, Sharon, were the budding breasts on Kiera’s thin little chest.  

For Kiera, whose last name is being withheld to protect her privacy, it was all so embarrassing. None of her friends seemed to be experiencing what she was. When they asked about the acne and her expanding chest, Kiera was evasive. “I didn’t want to tell them what was going on,” says the Pittsburgh girl, now age 9. “So I had to kind of lie to them.”“I thought, she’s too young,” remembers the Pittsburgh mom. “She’s still fearful about sleeping by herself. An 8-year-old just isn’t mature enough to handle this.”

When Kiera’s parents took their daughter to the doctor, he assured them that nothing was wrong with the girl. Kiera was simply starting puberty early.

As it turns out, puberty at age 7 or 8 isn’t so unusual these days. A new study, published Monday in the journal Pediatrics, shows that more American girls are maturing earlier and earlier. Typically, U.S. girls hit puberty around age 10 or 11.

Exactly what this shift means for girls isn’t clear yet — either on a group or individual level.  But there are budding concerns. For instance, studies have linked an early start to menstruation with an elevated risk of breast cancer. And other research has shown that girls who go through puberty early tend to have lower self-esteem and a poor body image. They are also more likely to engage in risky behaviors which can result in unplanned pregnancies, experts say.

The possible link to breast cancer was what sparked the new study. To take a long-term look at the impact of puberty and other factors on breast cancer, researchers enrolled 1,239 girls between the ages of 6 and 8 from three sites in the U.S.: New York’s East Harlem, the greater Cincinnati metropolitan area and the San Francisco Bay area.

The study revealed a surprisingly large bump in the number of girls going through puberty between the ages of 7 and 8. For example, the researches found that 10 percent of 7-year-old white girls had some breast development as compared to 5 percent in a study published in 1997. Similarly, 23 percent of the 7-year-old black girls had started puberty as compared to 15 percent in the 1997 study.

Nobody’s sure what is driving the declining age of puberty. But the rise in obesity could be at least partly to blame, says the study’s lead author, Dr. Frank Biro, director of adolescent medicine at Cincinnati Children’s Hospital.

That makes a lot of sense to Dr. Luigi Garibaldi, a professor of pediatrics and clinical director of pediatric endocrinology at Children’s Hospital of Pittsburgh at the University of Pittsburgh Medical Center.

Back in the 1700s, girls didn’t start to menstruate till they were 17 or 18, Garibaldi says. That had a lot to do with malnutrition. The assumption is that the steady decline in age since then has to do with more abundant food.

There may be other environmental factors at work, too, says Dr. Stanley Korenman, an endocrinologist at the University of California, Los Angeles.

For example, Korenman says, environmental exposure to estrogens in plastics, chemicals and foods has been going up. “And estrogens do stimulate breast development,” he adds.

Until we know what the cause is, the best way to slow puberty may be to “start living green,” says Biro. “It may help for families eat together and to consume well-balanced diets. Regular physical activity may help, too.”

Another finding from the study may back that concept up. The rate of early puberty was much lower in the San Francisco group: 7 percent among white 7-year-olds from northern California versus 14 percent among Ohioans of the same age. Among black 7-year olds, 27 percent of Californians hit puberty early as compared to 31 percent of the New Yorkers. Northern California’s temperate climate fosters more outdoor activities and the emphasis on healthy foods results in a better diet.

Why all the fuss about early puberty?

Beyond the possible breast cancer connection, there’s also the issue of emotional maturity, Biro says. “Just because a girl has matured physically, doesn’t mean she’s socially or psychologically mature,” he explains.

There’s also the issue of stature. There are some studies, Biro says, that show that kids who mature early don’t grow as tall.

As part of her work-up, Kiera had a bone exam. Doctors concluded that at age 8 she had the bone development of a 10 year old, which meant her growth might be stunted.

For Kiera and her family, the answer was simple: slow puberty down. She now has an implant placed under the skin of her upper arm that doles out regular doses of a drug that blocks the spiking hormones that were taking her into early sexual maturity.

Kiera was happy to see her breasts stop budding and to once again feel like she fits in with all her friends. These days she says she’d be perfectly happy if those breasts didn’t start to swell again till she was 16.