Tropez-Sims oversaw Meharry’s participation in a national study, published by Pediatrics last November, of more than 4,000 boys, showing that they too are entering puberty earlier. As a physician and researcher, she agrees with most scientists that more study is needed on why increasingly younger children are growing breasts, pubic hair and so forth, and whether hormone-infused foods play a role.

Absent any rock-solid answers on that front, researchers have explored other causes. Some studies, including one in the February 2008 issue of Pediatrics, have suggested that obesity is a driver of early onset puberty. But that doesn’t explain what transpired with Kayla, who was a reed-thin second-grader. Now 15 and a liturgical dancer at her family’s church, she stands at 5’ 6” and weighs a lean 120 pounds.

“In the 19th Century, the age of menarche was 15,” Tropez-Sims said. “Today, we may be looking at environmental chemicals, steroids and so on that are causing puberty to begin in progressively younger kids. And it seems reasonable to ask this question: If they’re feeding pigs and cows and chickens growth hormones and other chemicals to make them plumper, bigger, is that also making our kids plumper, making them mature faster? … There’s not been enough science to fully link hormones in the meat, but some of us are extrapolating that that’s just what may be happening.”

Tracking children who eat no hormone-laden foods against those whose diets are full of them would provide the most conclusive proof of what’s going on, she said. But such a study has never been conducted. And doing one raises ethical concerns, given what some consider the potential risks faced by children in the latter group, Tropez-Sims added.

“Who will enroll their daughter in a study where they might be randomized to a diet high in food with hormones that can negatively impact health?” asks Dr. Peter Tebben, an endocrinologist specializing in pediatric and adolescent medicine at the Mayo Clinic in Rochester, Minn. “A lot of the controversy around this subject [exists] because we simply don’t have all the answers.”

What is certain, he said, is that getting one’s period earlier raises one’s lifetime exposure to estrogen and, consequently, for developing breast cancer.

“On the flip side, estrogen is good for bone health … But that probably would not outweigh your concern about breast cancer,” Tebben said.

Apart from that risk, he continued, there’s “the psycho-social issue of starting to menstruate in first or second grade” and, especially for girls, the challenge of looking older than they actually are.

Another concern, Tropez-Sims said, is the risk that some kids, given that early puberty stirs the libido, also will become sexually active too soon.

Premature puberty can be interrupted with monthly, quarterly or yearly shots of drugs such as leuprolide, a synthetic hormone that suppresses natural hormones controlling puberty. That was the kind of option McDonald-Haye was unwilling to entertain. Even in hindsight, she believes she made the right decision.

“Kayla didn’t have any additional [breast] tissue growth for another two years,” McDonald-Haye recalled.

During her daughter’s next yearly check-up, the pediatrician who’d identified the prematurely developing breast tissue was surprised by Kayla’s physical appearance. “She was, like, ‘Wow.’ She thought Kayla’s breasts would have been much larger by then,” McDonald-Haye said.

She continued: “I’m not a scientist. I cannot give you the language that a doctor would. But, when Kayla was seven, with those little buds just beginning to show, I was thinking long-term about what all of this means for my child. I wanted her to be healthy, and for her body to do what it does naturally. If some unnatural things were getting in the way of that, I also wanted to be proactive.”

New York-based freelancer Katti Gray specializes in reporting health, higher education and criminal justice. Her byline has appeared in The Washington Post, Salon, Reuters, Newsday, Ms., Essence, Ebony, CNN.com, ABCNews.com and other national and regional publications. Follow her on twitter @KattiGray.