Briefly,
There are 2 different types of bones, long and flat.
Long bones; arms/legs have growth plates that seal and determine how tall you are and how long your limbs are. HGH can not make them grow. Flat bones; hands, feet face, knee caps and elbows will grow with HGH usage, that is why foot size increases and head/face gets distorted.
Pretty harmless, however, organs like the heart grow as well, leading to specific types of cardiomegaly that are fatal.
Organ growth, liver etc is why abdominal distention is so common, that is why this lifestyle is so F'd.
Hope this helps.