While most are stunned by the news that a 9-year-old girl who had been raped gave birth in Mexico, doctors have known for years that the average age of puberty is declining.

A landmark 1997 study in the journal Pediatrics prompted a redefinition of early onset puberty, from 8 to 7 among Caucasian girls and 7 to 6 among African-American girls for early breast development.

While age of puberty is decreasing, the number of girls entering puberty early is increasing: about 16 percent of girls enter puberty by the age of 7, and about 30 percent by the age of 8, according to one study.

The main question is, Why?

A study publishedrecentlyin the journal Nature Neuroscience seems to have fit another piece into the puzzle, when researchers were able to delay puberty in female rats by manipulating protein levels. They discovered a group of proteins that regulate the activity of a gene called the Kiss1 gene, which is required for puberty to occur.

Study author Serjio Ojeda, a neuroscientist and professor in the Oregon Health & Science UniversitySchool of Medicine, says that his teams findings raise the possibility that environmental factors play a role in early onset puberty.

"It poses the question as to how are these epigenetic mechanisms responding to the environment?" he said. "These are difficult questions we haven't answered yet. Is it nutrition, man-made chemicals? That's the next step, how can we connect these environmental stimuli?"

"That's the crystal ball question," agrees Dr. William Crowley, Professor of Medicine at Harvard Medical School, the Chief of the Reproductive Endocrine Unit of the Department of Medicine at Massachusetts General Hospital, who has studied early onset puberty for 35 years but was not involved in Ojeda's study.

The research is starting to coalesce, he said.

"The tipping point is very close," he said. "It's like when you're paddling down a great river and it gets very quiet just before the falls, and it looks pretty benign until you start to hear a dull roar. That's the kind of sense everybody has right now; you can kind of hear a dull roar."

Continued here:
What Causes Early Puberty in Girls?