papillary thyroid cancer.
I have a friend who had this at 30.
It's nbd -- one of the weakest types of cancer, with survival rates >99% in the young. My friend is still in the gym, looking good, and making gainz without a thyroid.
But he had to come off HGH permanently and forever. This kind of thyroid cancer is only dangerous when it spreads to other organs, and HGH facilitates that.
It probably wouldn't have killed him, but Dallas' career as a pro would have been over as soon as his docs discovered his thyroid cancer. Not that it matters.