At least five openly transgender women have signed up to run in the Boston Marathon, the Boston Herald is reporting.

While they are not the first transgender runners to compete in the marathon, the decision to enter the race is still sparking controversy, the newspaper noted. Some question whether runners who identify as women, but were born males, could have a competitive advantage, according to the Herald.

“We take people at their word,” said Tom Grilk, chief of the Boston Athletic Association, the group behind the race. “We register people as they specify themselves to be. Members of the LGBT community have had a lot to deal with over the years, and we’d rather not add to that burden.”

But Bob Girandola, associate professor in the Department of Human Biology at the University of Southern California, said it is a possible issue if transgender runners produce higher levels of testosterone than their female competitors.

“Maybe they have to have a separate category if they’re going to do that,” he said. “It’s a dilemma.”

But others are in sharp disagreement.

“That’s a misconception and a myth,” said Dr. Alex Keuroghlian, director of education and training programs at the Fenway Institute, a health and advocacy center for Boston’s LGBT community. “There’s no physiologic advantage to being assigned male at birth.”

NPR reported the athletic association has no specific policy on transgender runners. However, runners have been asked in the past to compete in the marathon with the same gender identify which they qualified.

And the athletic association said: “We don’t require that runners outline their gender identity history with us, so we can’t say for certain how many trans runners are in our race. We do know that we have had several transgender runners in the past.”

The marathon is scheduled for April 16.