A new study from the journal Pediatrics finds that girls are beginning to develop breasts at the early age of 7 or 8.  These results support the findings of a 1997 study that noted puberty beginning in girls at the age of 7 or 8.  But why are our children starting puberty so much earlier?  Evidence indicates that the increasing rates of obesity play a major role.

According to current medical understanding, puberty normally begins in girls between ages 8 and 12 and in boys between ages 9 and 14. Historically, “precocious puberty” (early-onset puberty) has been defined as before the age of 8 for a girl and before the age of 9 for a boy.  The beginning of puberty is marked by penile enlargement or pubic hair growth for boys and breast bud formation and pubic hair growth for girls.  If a child shows such signs of puberty before this age, she is sent to a pediatric endocrinologist for a full workup.

Why does obesity lead to early-onset puberty?  Adipose (fat) tissue is metabolically active; fat tissue produces estrogen.  The more fat tissue a child has, the more estrogen she is exposed to.  It is generally accepted that overweight kids begin puberty earlier for this reason.

The presence of increased amounts of environment chemicals that mimic the effects of the sex hormones may also speed up the onset of puberty.  To date, there is no evidence to prove that assumption.   Dr. Frank M. Biro, the author of this new study, believes environmental chemicals are playing a role and will begin studying girls’ hormone levels and lab tests measuring their exposures to various chemicals.  More research needs to be done before we can conclusively state that these chemicals are affecting our children.

Early-onset puberty can lead to medical problems.  Girls who begin menstruating early have a slightly increased risk of breast cancer than other girls; such girls have a longer lifetime exposure to estrogen and progesterone, which can increase the growth of certain tumors.  While this study looked at breast growth and not menstruation, breast growth is also a sign of hormone exposure and likely also indicates an increased risk of cancer.

Kids with early-onset puberty also suffer from short stature.  While they initially appear taller than their peers, their growth plates close early, preventing the attainment of normal height.   The child who was the tallest in her class soon becomes shorter than her friends.

Girls with early puberty are also more likely to have polycystic ovarian syndrome (PCOS).  PCOS is a hormone disorder that begins in puberty and causes infertility, acne, and other endocrine abnormalities.

The onset of puberty differs among races.  African American and Hispanic children often begin puberty earlier than kids of other races, even when weight is taken into account.  This differential was confirmed in the current study.  While all kids seemed to enter puberty earlier, African American and Hispanic children began the earliest.

Not all doctors agree with the results of this study.  Dr. Catherine Gordon, a pediatric endocrinologist and specialist in adolescent medicine at Children’s Hospital Boston, said that so far, most evidence showed that neither breast development nor menstrual age had changed for white girls of normal weight.  Yet according to Dr. Biro, “our analysis shows clearly that the white participants entered puberty earlier than we anticipated.”

The new study included 1,239 girls ages 6 to 8 who were recruited from schools and examined at one of three sites: the Mount Sinai School of Medicine in Manhattan, Cincinnati Children’s Hospital or Kaiser Permanente Northern California/University of California, San Francisco. The group was roughly 30 percent each white, black and Hispanic, and about 5 percent Asian.

At 7 years, 10.4 percent of white, 23.4 percent of black and 14.9 percent of Hispanic girls had enough breast development to be considered at the onset of puberty.

At age 8, the figures were 18.3 percent in whites, 42.9 percent in blacks and 30.9 percent in Hispanics. The percentages for blacks and whites were even higher than those found by the 1997 study that was one of the first to suggest that puberty was occurring earlier in girls.

The question remains, when should doctors refer a child for a precocious puberty workup?  Some endocrinologists worry that if we accept puberty beginning at age 7 or 8 we would overlook serious medical problems, like endocrine diseases and tumors.  On the other hand, if this earlier puberty is the new norm, why should we frighten families and waste valuable time and money on unnecessary tests?  At this time, current practice does warrant a workup for any girl who shows signs of puberty before age 8.

It is clear that early-onset puberty is just one more effect of the child obesity epidemic.  It is imperative that we help our overweight children attain a healthy weight as soon as possible.  Parents are urged to get help for their overweight kids as soon as they begin to show signs of abnormal weight gain.

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