I knew baseball allows Doctor-approved use of some banned substances. I didn't know some players are allowed to use Testosterone:
Under baseball’s performance-enhancing drug policy, players can apply for a so-called therapeutic use exemption (TUE) to take certain medical substances otherwise banned by MLB. A doctor appointed by both sides—the independent program administrator (IPA) -- reviews all applications. Baseball also has an expert medical panel to advise the IPA. If an exemption is granted, the player cannot be punished for using that substance. The exemption is good for one year.
Before the 2007 season, Rodriguez asked for permission to use testosterone, which has been banned by baseball since 2003. The IPA in '07 was Bryan W. Smith, a High Point, N.C., physician. (Baseball did not yet have the advisory medical panel.) On Feb. 16, 2007, two days before Rodriguez reported to spring training, Smith granted the exemption, allowing Rodriguez to use testosterone all season.
Statistics requested in 2008 by Massachusetts congressman John Tierney as part of a government probe into baseball’s PED problem reveal how rare testosterone exemptions are. In 2007, of the 1,354 players subjected to testing, 111 were granted a TUE. Only two, apparently including Rodriguez, received an exemption for “androgen deficiency medications,” the category that would include testosterone. The other exemptions that year involved treatments for baldness, hypertension and -- predominantly -- attention deficit disorder. The alarmingly high number of exemptions for the latter was Tierney’s main concern. “I think it begs a question: Are people using this as a loophole?” said Tierney. “Are they taking these because they are perceived as a performance-enhancing drug, or do they have a legitimate medicinal purpose?”