HGH exhibits its effect on pancreatic beta cells, promoting enhanced insulin secretion which usually exhibits itself to some degree as hyperinsulinemia.

This can lead to a degree of insulin resistance and possibly the development of type 2 diabetes. No different really as to the cause of the hyperinsulinemia, either HGH mediated or due to constantly elveated levels of Blood Glucose causing this state...

The best thing is to be able to monitor and manage BG. GDAs, Low GI diet, etc to reduce the possibility.