DALLAS — Over the last few decades, the childhood of American girls has shortened significantly. Some studies indicate girls are maturing physically two years earlier.

Emilie Nelsen is like most seven-year olds, but taller, by her own admission.

"Some kids say, 'Wow, are you in 3rd or 4th grade?'" Emilie said. "I'm like, 'No, I'm in first, really.'"

Long before she should have, Emilie's body started maturing in other ways, too.

"She had early breast development," said Melissa Nelson, Emilie's mother. "We didn't wear clothes that were tight-fitting so I didn't make her stand out from the other kids. We kept that hid. And it worked out very well. Most people didn't know at all."

Some blame hormones in milk and meat for earlier maturity. Others cite chemicals in plastics.

Obesity can also be a cause.

"By far the most common cause is, we don't know why some children go into puberty early," said Dr. Paul Thornton, a pediatric endocrinologist who specializes in precocious puberty.

Dr. Thornton said a non-cancerous brain tumor triggered Emilie's hormones to go haywire.

Not long ago, Cook Children's Medical Center in Fort Worth began trying a new treatment to slow down early puberty.

Supprelin LA is a one-inch plastic tube that is embedded into a patient's arm. It looks like a birth control implant, except it supresses hormones continuously.

"The drug slowly escapes from the implant and supresses puberty for over a year," Dr. Thornton explained.

Dr. Thornton said treating early puberty can make a huge difference for a child. "If you go into puberty early, it can impair your final adult height," he said. "And so while these children may be taller when they're younger, they end up shorter as adults."

The puberty implant isn't for everyone. Overweight children should try to lose weight first, because Supprelin LA can cause weight gain.

Emilie's mother said the implant eliminated wild mood swings that went along with raging hormones in her child.

"Getting the implant, it changed our lives," Melissa Nelson said. "I mean, she's a new kid — totally new kid."

And Emilie's body now looks less like a 17-year-old's and more like the seven-year-old she is.

E-mail jstjames@wfaa.com