There is an official IOC document but a quick search pulled up this on cbc
"Under the previous IOC guidelines, approved in 2003, athletes who transitioned from male to female or vice versa were required to have reassignment surgery followed by at least two years of hormone therapy in order to be eligible to compete.
Now, surgery will no longer be required, with female-to-male transgender athletes eligible to take part in men's competitions "without restriction."
Meanwhile, male-to-female transgender athletes will need to demonstrate that their testosterone level has been below a certain cutoff point for at least one year before their first competition"
http://www.cbc.ca/sports/olympics/ioc-transgender-athletes-guidlines-1.3417794