Earlier Puberty in Girls – New study, why care?

While working with fellow residents in the adolescent medicine department at Cincinnati Children’s Hospital, we would bring our difficult patient cases to our attending physician, Dr. Frank Biro. His infamous and familiar response to our inquiry was always, “I don’t know.  I’m just a simple country doc.”  This response would leave us grumbling back to our medical texts and computer searches to find the answer he obviously knew.

It is certainly not surprising that Dr. Biro is the lead author of a significant new article to be published in the September issue of PediatricsThe article reveals an increased percentage of girls aged 7 to 8 beginning breast development than girls of a similar age 10-30 years earlier.

Why was this study conducted? And why should we care?

Dr. Biro’s newest study is focused on the timing of breast development.  This physical change is the beginning puberty. Past analyses of women with breast cancer indicate early puberty onset as a risk factor for developing breast cancer.  With this concern, the Breast Cancer and the Environment Research Centers (BCERC) directed study to determine the onset of breast development  in 7 to 8 year old females.

This study is significant in regards to how the subject’s pubertal development was determined. Assigning pubertal staging can be difficult. Although there have been previous studies reporting an increased rate of pubertal onset in younger females, some of these studies have been criticised for not having reliable and consistent methods to grade subjects’ pubertal stage.  This new study did extensive analysis of puberty rating between different clinicians in order to optimize the reliability of the results.

The research was conducted in 3 different facilities.  After extensive training on “Tanner staging”, the researchers documented breast development occurring in 10.4% of white, 23.4% of black, and 14.9% of hispanic 7-year olds (race was declared by parent or guardian).  At 8 years, development was seen in 18.3%, 42.9%, and 30.9% respectively. These percentages were reported after extensive analysis of the researcher’s ability to correctly and reliably stage the subject’s breast development.  The percentages in this paper are greater than girls of similar age 10-30 years earlier.

Earlier puberty comes with a emotional and physical cost. Girls with early breast development have a tendency to identify with older peer counterparts.  This, in turn, may expose girls to social situations in which they are unprepared.  A girl with the cognitive development of a young child is not mature enough to handle sexual advances from the opposite sex or the emotional changes associated with those situations.  Girls with earlier maturation are also at an increased risk of eating disorders, decreased self-esteem, and depression.  Physically, early puberty is associated with an increased rate of breast and endometrial cancer.

There is much interest in the factors initiating puberty.  Onset is a blend of genetics and environmental exposures.  It is also known that body fatness is associated with earlier puberty onset compared to “average” weight counterparts.  Routinely visiting a pediatrician to discuss body measurements is an important part of determining normal growth.  BMI can be calculated after body measurements are taken.  An increased BMI reflects an increased percentage of fat mass.  Fat cells are known to contribute to the conversion of inactive sex hormones to their active states.  Therefore, more fat implies more sex hormone availability.  This association presents additional evidence of the importance of maintaining a healthy body weight for our pre-teen girls.

A girl’s weight, however, is certainly not the only factor in determining puberty onset.  There seems to be environmental triggers important to the onset as well.  Some of these outcomes associated with early puberty have been suggested to be caused by exposure to chemicals mimicking hormonal or metabolic processes.

It is of significant note, however, that despite this paper suggesting an earlier age for the beginning of puberty, the average age of girls’ first menstrual period is remaining the same.  It is possible that earlier breast development may be a reflection of “healthier” children, meaning children with better hygiene, clean water access, less sickness due to vaccinations and medications, and better access to food.  Is this a sign of cultural progress?

This research is influential in gaining addition research dollars to explore the environmental exposures potentially influencing pubertal change.  In addition, changing what is considered “normal” pubertal development may affect clinical guidelines testing females with breast development at an earlier age.  This is important knowledge for pediatricians, saving the patient and her family much financial and emotional stress.

There is no doubt that this “country doc” is on to something.  I will be looking to hearing more from Dr. Biro and his team in the near future.