He was one of two players granted a therapeutic use exemption.
According to the new book, Blood Sport: Alex Rodriguez, Biogenesis and the Quest to End Baseball's Steroid Era, and excerpted on SI.com, former Yankees third baseman Alex Rodriguez was granted a therapeutic use exemption (TUE) for testosterone from MLB before the 2007 season.
The exemption is granted by an independent program administrator (IPA), and was one of two TUEs made for "androgen deficiency medications." There's no stated reason for why Rodriguez required the exemption, but it wasn't the only one he requested over the years. He received a TUE for clomiphene citrate and was denied a TUE for human chorionic gonadotrophin, both of which relate to testosterone.
MLB released a statement in response to the news about Rodriguez's TUE, stating
All decisions regarding whether a player shall receive a therapeutic use exemption (TUE) under the Joint Drug Program are made by the Independent Program Administrator (IPA) in consultation with outside medical experts, with no input by either the Office of the Commissioner or the Players Association. The process is confidentially administered by the IPA, and MLB and the MLBPA are not even made aware of which players applied for TUEs.
They reiterated that the granting of TUEs for performance-enhancing substances is extremely strict, and compared the process to that of the World Anti-Doping Code. Since 2008, under a recommendation from the Mitchell Report, MLB and MLBPA have issued an annual report from the IPA stating how many exemptions are granted under each category of medication. This indicates that MLB itself might have been unaware of how many or who received exemptions before 2008, when Rodriguez would have received his TUE.
In 2007, Rodriguez batted .314/.422/.645 with 54 home runs, 156 RBI, 143 runs, and went 24/28 in stolen bases. He won his third MVP award en route to opting out of his contract with the Yankees only to re-sign for 10 years and $275 million.