HITH is a condition that normally effects fish such as discus and oscars, I've not heard of a gourami giant or otherwise being affected by it but I've been wrong before. There are many theories about what causes it but the main way too avoid it IMO is keeping stress levels down by providing good clean water in suitable tanks, with a good diet. I also keep discus and never had any cases in many years. I have also had many different various non giant gouramis in the past again without this condition.
Just noticed that was directed at Lou, anyway It'll save him typing the same thing with 2 hands