This is not about tennis per se, but it is a positive step for a big league to implement this:
http://www.nytimes.com/2015/04/17/sports/basketball/nba-to-test-players-for-hgh-starting-next-season.html?ref=basketball&_r=0
http://www.nytimes.com/2015/04/17/sports/basketball/nba-to-test-players-for-hgh-starting-next-season.html?ref=basketball&_r=0