Some heath experts are concerned androstenedione could carry the same health risks as steroids.

NEW YORK (CNN) -- Although sports network ESPN has pulled ads for a controversial supplement off its air, the debate over muscle-building androstenedione is far from over.

Steroids and muscle enhancers have been around for years, but the hormone androstenedione has only recently gained notoriety with Cardinals star slugger Mark McGwire's acknowledgement that he has been using the substance for more than a year.

Sales have jumped dramatically with some retailers reporting five-fold increases.

"Sales have practically doubled since this whole Mark McGwire thing has happened," said John Matist, director of operations for supplement seller Smoothie King.

Despite its popularity, the supplement is under fire.

Some health experts say taking it could have dangerous consequences similar to those of steroids, and there is a growing fear it could be abused by teen-age athletes.

The hormone, which is produced naturally in the body, increases levels of testosterone that help build muscle.

Although androstenedione is allowed in professional baseball, its use is banned by the NFL, the National Collegiate Athletic Association and the Olympics.

The television ad campaign for MetRx's androstenedione product first aired Tuesday on ESPN before it was pulled by the network.

Some high schools, such as Nazareth High School in Brooklyn, New York, are forbidding it.

Its athletic director, Bob Myers, said he was disappointed with the ESPN, a network many of his students enjoy watching.

"I'm appalled by it," he said. "I'm appalled that they advertise it."

Supplement maker MetRx started a television ad campaign for androstenedione this week with its first commercial first appearing Tuesday during the ESPN's program, "American Muscle."

But ESPN pulled the ads Wednesday after heavy criticism from the NCAA and the National Federation of State High Schools Associations.

"Given the debate in the medical and sports community, we have decided for now not to run androstenedione ads," the network stated.

"We have to be careful with our young student athletes and make sure that we are providing them with enough sound information to make good judgments," said Cindy Thomas, assistant director of sports scientists for the NCAA.

MetRx has defended its ads, saying product labels warn the supplement should not be used by children under age 18.

CNN New York Correspondent Gary Tuchman and The Associated Press contributed to this report.