As everyone says, the guy's been megadosing very powerful hormones/drugs for many years. Resilient or not, the human body can only take so much abuse before various systems and organs go south.
Look at Branch. There's a guy whose body is at full-on revolt status. Literally deteriorating and wasting before our eyes, contest to contest.
Heath's freaky, sure, but his proportions are all off, and, regarding the original point of the thread, unquestionably his face and physique are morphing. And not in a good way.
His cock neck and googly eyes are particularly concerning.