The AP cited "a person familiar with the details of the suspension" as saying that Ramirez tested positive for human chorionic gonadotropin (HCG) during Spring Training.
"HCG, added to baseball's banned substances list last year, is popular among users of performance-enhancing drugs because it can mitigate the side effects of ending a cycle of steroids," The AP wrote. "The body may stop producing testosterone when a user goes off steroids, which can cause sperm counts to decrease and testicles to shrink."
Ruth Wood, a steroid expert from the University of Southern California, told The AP, "They use [HCG] to essentially jump start testosterone production."
Meanwhile, Dr. Gary Wadler, who helps make the banned-substance list for the World Anti-Doping Agency (WADA), said HCG also has legitimate uses that aren't related to steroids, such as treating male infertility and deficiencies in testosterone levels.
"It's not necessarily the drug of choice, but those are acceptable uses," Wadler told The AP.
In his statement following the suspension, Ramirez said, that the HCG positive was a result of medical treatment for "a personal health issue."
U.S. Anti-Doping Agency CEO Travis Tygart questioned Ramirez's claim in an interview with The AP, saying, "We have no knowledge of the Ramirez case, but it's highly unlikely an otherwise healthy, young athlete would need HCG for a legitimate medical reason.
"That said, if there was valid medical need, his high-priced representatives should be fired for not ensuring that he was informed of the process that could have granted him permission to use it."
Wadler told The AP that HCG side effects "include headache, mood swings and depression."
Doug Miller is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.