Girls as young as 6 or 7 years old who display the first signs of puberty are in many cases normal and do not routinely require workups by specialists or injections of hormones to delay maturation, according to new recommendations by endocrinologists.
The guidelines, which are likely to prove influential among the nation's pediatricians, appear in the current issue of Pediatrics, the journal of the American Academy of Pediatrics. They represent a significant change in what doctors have considered to be a normal age for starting puberty--a process that doctors say is beginning earlier for girls, but not for boys.
"Some parents truly are shocked when their 7 1/2-year-old daughter starts developing breasts," said Paul B. Kaplowitz, a pediatric endocrinologist at the Medical College of Virginia, co-chairman of the panel that wrote the guidelines. "We're definitely seeing more of this and nobody really knows why. These recommendations reflect a realization that the standards we've been using for puberty are really out of date."
For decades, doctors have routinely diagnosed girls younger than 8 as having "precocious puberty" if they showed signs of maturation, such as breast development. Typically such girls have been referred to endocrinologists for a complete workup to rule out a hormonal problem or brain tumor. But in most girls who begin puberty between the ages of 6 and 8, no disorder is found.
The recommendations, which represent a consensus of opinion of the nation's pediatric endocrinologists, state that African American girls 6 or older and white girls older than 7 with beginning breast development or pubic hair do not need routine workups for precocious puberty if no other signs of sexual maturation--genital enlargement, acne or growth acceleration--are present.
Since 1979 many girls with early puberty have been aggressively treated with expensive monthly hormone shots that shut down and even reverse puberty and, it was hoped, prevented them from becoming abnormally short adults. Typically girls grow an average of 3 1/2 inches after their first menstrual period. Doctors have worried that girls who started puberty in first or second grade would menstruate earlier and might not reach normal height in adulthood.
But such drug treatment may be abandoned. The panel noted that most girls who begin puberty early are tall for their age and that hormone shots had no significant effect on their adult height. Girls who started puberty early reached normal stature without treatment, the panel concluded after reviewing scientific studies.
The endocrinologists' guidelines are based primarily on a study of more than 17,000 girls between the ages of 3 and 12 that was published two years ago. Marcia E. Herman-Giddens, an associate professor of public health at the University of North Carolina, and her team surveyed more than 200 pediatricians' offices around the country and found that by age 8, 48 percent of black girls and nearly 15 percent of whites had begun to develop. The reason for the racial disparity is unclear.
Herman-Giddens's study, the most comprehensive of its kind, documented what many doctors said they had been seeing in their offices: that among American girls, puberty was occurring much earlier than standard medical textbooks indicated. Those textbooks reflected standards established in the 1960s and were based on research conducted in Britain involving 192 girls who lived in an orphanage.
Although puberty may be starting earlier for girls, some aspects of it have not changed. The age of menarche, when girls first menstruate, has not changed in the past 50 years, Kaplowitz and others say. White girls on average get their first period at 12.8 years; for African Americans the average age is 12.1.
"It's almost as though puberty has been spread out," Kaplowitz said. "The earlier puberty starts, the longer it takes to complete."
Kaplowitz and his colleagues speculated that girls with early puberty may have a "more slowly progressive form of puberty" and their bone development is not accelerated.
Experts say that studies are underway to determine the reasons for earlier maturation. Some experts believe it may be due to environmental changes, such as the use of pesticides, or hormones and hormone-like substances known as "endocrine disrupters."
Kaplowitz believes that obesity, particularly among white girls, is a key factor. Among black girls, the relationship is less clear-cut, he said, and some researchers believe that genetic factors may be more influential among African Americans.
"I think at least part of the explanation is overweight," said Kaplowitz, who is preparing to publish a study on body mass index and early puberty. "We're also seeing a lot more type II diabetes in young girls, which used to be extremely rare." Type II diabetes typically develops in adults over 40, particularly if they are overweight.
One explanation for earlier puberty, Kaplowitz said, may be that some girls have a surfeit of leptin, a hormone manufactured by fat cells. A certain amount of body fat is required for normal reproductive function, and an abundance of leptin might contribute to earlier maturation. "It makes sense evolutionarily, because if you were very underweight you couldn't sustain a pregnancy."
While early puberty may be normal, pediatricians say that fact doesn't make it much easier for young girls or their families.
"There's no evidence that these kids are developing earlier cognitively," said David W. Kaplan, a professor of pediatrics at the University of Colorado School of Medicine and chief of adolescent medicine at Children's Hospital in Denver. "I think a fair number of girls have a tough time of it. They're often embarrassed and boys start treating them differently. These kids are very young."