Growing Up Too Fast: Precocious Puberty's Gene Link

According to research first published in the journal Pediatrics in April 1997, the average age at which girls hit puberty may be falling. Researchers found that the average age for breast development or the growth of pubic hair was 9.7 years old for Caucasian girls and 8.1 years old for African-American girls.

A number of theories have emerged in an attempt to explain the trend. Dr. Robert Lustig, professor of pediatric endocrinology at the University of California at San Francisco, says that when it comes to the vast majority of these cases that are not genetic in origin, the chain of events that leads to early puberty is usually initiated between the ages of 6 and 8.

"In these cases, estrogens and other organic pollutants in the environment may be a more important issue [than gene mutations]," Lustig says. But, he adds, "obesity seems to be the most significant contributor to the 'epidemic' of precocious puberty, as [fat] tissue produces estrogen, which then causes breast development."

But other explanations abound. In a study released last November, for example, researchers at the University of Arizona found evidence that a stressful family environment may cause puberty to kick in early for young girls.

Still, if one thing remains clear, it is that any increase in the trend likely has little to do with genetic mutations.

"If precocious puberty has been increasing in frequency over the last few decades, it cannot be based on genetic changes," says Dr. Neil H. White, professor of pediatrics and medicine at the Washington University in St. Louis School of Medicine. "Changes in disease frequency as a result of genetics requires a long time and does not occur over a couple of decades."

Potentially Useful Genetic Trigger

Since the genetic mutation uncovered by Kaiser and her colleagues is so rare, a diagnostic test to detect the gene mutation would probably be of little use to parents who wanted to assess their children's risk of early puberty.

"For this to be useful in preventing cases of precocious puberty, this gene would have to be a common enough cause of precocious puberty to justify screening all children for this gene," Groshek says. "Whether this gene is unique to this girl or is found in others is not clear. It certainly is not common, based on this team's findings. So I don't see it having any potential at this time to help us find kids who are prone to precocious puberty."

Still, the finding may be useful on the therapeutic level, Kaiser says. Specifically, if doctors could find a way to manipulate this genetic switch, they may be able to exploit it to treat patients who suffer from early puberty or other reproductive problems — including infertility.

"We may eventually be able to tinker with the switch to induce fertility, or turn it off if you wish to switch off this pathway," she says.

And she says the research suggests the possibility that there are more such mutated genes out there that could lead to the condition.

"Probably this is really the tip of the iceberg," Kaiser says. "The genes involved in the timing of puberty are just now being uncovered.

"So while we're not so sure that this mutation is necessarily so common, it is a prototype for the genetic contributors to early puberty."

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