human growth hormone - somatropin - denatures irreversibly however and so heat denaturing without any noticable renaturing of the native and active protein structure would show that the human growth hormone - somatropin - was in fact real. Yes, the human growth hormone - somatropin - could be substituted with other heat sensetive proteins that don't reversibly renature, but these proteins are exclusively used in research. I can tell you from experience that such proteins are far more expensive than human growth hormone - somatropin - . This would make sense since they are just as difficult to extract in active form, and are not being used by hundreds of thousands of people for medical purposes.
So, bottom line; if you have a protein that denatures in heat irreversably, it is either human growth hormone - somatropin - , or an enzyme/protein that is at least as expensive (more likely a lot more expensive).