I believe he was very weak, and under developed .. Its the opposite to what andre the giant did to prevent him from becoming ill ..
Its a steroid i believe, but steroids can be used for health benefits .. In thiscase, it helped messi fulfill his potential, he would have been a foot shorter had he not had the treatment
The argentinan club couldnt afford it, lucky fot messi, his talent meant that barce saw $150k treatment a year for his health bein justified because of jis ability .. Glad they did so
Though the board almost ruined the transfer by refusing to offer him school boy terms originally, as they had a fued with a coach and scout who worked with bringing messi over.. His first pre agreement being signed on a cafe napkin!
Or does messi still use it today!