The Los Angeles Dodgers outfielder received a 50-game suspension May 7 for violating baseball's substance abuse policy.
The ESPN cable sports network reported that 71-year-old Pedro Publio Bosch was the doctor at the center of a Drug Enforcement Agency investigation and that his son, Anthony Bosch, 45, is alleged to have worked as a contact between him and Ramirez.
Ramirez said he took a female fertility drug.
ESPN also said Bosch is well-known in Latin American baseball circles and that his relationship with players dates back to at least the early part of the decade.
Major League spokesman Pat Courtney told the Los Angeles Times baseball is aware of the investigation and is cooperating with the DEA.
Ramirez is eligible to return on July 3, but is playing rehabilitation games at Albuquerque, the Triple-A minor league affiliate of the Dodgers.