China government does the same thing that Russia does. They pick tall people at an early age... and basically kidnap them to ensure they play sports/basketball... and they also make sure they mate with other freakishly tall people as well...
This is what happened with Yao... He is basically part of their breeding program....
But this is different from Giganticism... which is extremely rare... its caused by a benign tumor in the brain which causes people who would normally be regular height to become 8' tall. The hospital I go to actually treats these poor victims.