Captain America is a super soldier in many ways. Dedicated to serve his country, he was willing to do whatever it took after failing a simple Army physical. It was his spirit and belief in America that made him the perfect candidate for Project Rebirth. Steve Rogers was the first and only candidate to take part in the experimental procedure.
Because Dr. Erskine was killed right after Steve was transformed, he never had the chance to get a full examination. It's likely that he did undergo several tests and examinations by others but because Erskine was the only one that knew the formula, he's the only one that would truly know how the transformation could affect Rogers.
Captain America spent several decades in a cryogenic state. It's believed that the Super Soldier Serum could be part of what allowed him to easily be revived from his frozen state. Because the full effects were never really considered, what would happen if the Serum suddenly wore off. What effects would it have on Captain America's body and his mission to serve his country?== TEASER ==
The question of whether or not it's the serum that makes him Captain America has been brought up before. His body was enhanced to perfection but it's more than just the serum that elevated him to the hero he is today. There have even been moments when it appeared Cap was losing the abilities given to him by the serum.
Back in CAPTAIN AMERICA #300, Cap faced the Red Skull in a hidden bunker. This was the be the Skull's final battle because he was dying. The effects from being in suspended animation on the Red Skull were wearing off and he was dying. His final act was meant to be the end of Captain America by his hands. He poisoned Cap, who found himself an old man but that didn't stop him. There was still enough spirit in him to fight the Red Skull.
There was also a time when Steve's body began to lock up (CAPTAIN AMERICA #438). Cap apparently had pushed the Super Soldier Serum past its limits. His body crashed and he was left paralyzed until Tony Stark implanted bio-chips into his neural system. He needed an exoskeleton suit in order to move.
He was now on borrowed time as his body would soon completely shut down which would lead to his death. Cap continued to do his duty and fight against evil. He knew continuing to fight would mean the end of his life but he couldn't simply sit back and do nothing.
To save him, the Super Soldier Serum was flushed from his system despite the serum being bonded with his blood. It turned out that Cap had received a blood transfusion from the Red Skull, whose mind was in a cloned body of Steve Rogers. It was later written that the serum had actually changed Cap's genetic make up. This explained how the cloned body the Red Skull used also had the affects of the Super Soldier Serum. Now we're faced with the question, can the serum actually wear off if it's already changed his genetics?
If Cap's DNA has been altered, this is who he is now. It shouldn't be possible for him to revert back to a normal state. The possibility of his age catching up with him also shouldn't be an issue since he was in a state of suspended animation for decades. Despite this idea, we're seeing Cap somehow temporarily revert back and losing his enhanced physique.
While he has mentioned he never wanted to be a leader or symbol, it's become such a large part of who he is. Even when he decided Bucky had to remain in the role of Captain America after Steve returned from the 'dead,' he became "Commander" Rogers and was leading what used to be the S.H.I.E.L.D. organization.
If Cap lost his Super Soldier Serum abilities, there's no way he would simply retire and try to live a normal life. Provided his body didn't suffer any incapacitating affects, Steve would have no choice but to continue serving and fighting off any evil forces that threatened the country. As long as he didn't lose his mental facilities, he could still serve as a commander or strategist. Cap will serve until the day he dies.
Another aspect of the Super Soldier Serum which hasn't really been touched on, besides in EARTH X, is how his body ages. He doesn't show signs of his true age due to being in suspended animation. If the serum made him essentially the perfect human specimen, what does that mean for the way it ages?
If his body is capable of doing extraordinary feats, perhaps it also handles aging in a different manner. People age as their cells break down. It's possible his body, being near perfect, is able to fight the effects of aging. He wouldn't necessarily be immortal but longevity could easily be possible. This would allow him to continue fighting longer than people would expect.
Captain America might not have the time for it but it would be in his best interest to get some of the smartest people around to finally figure out what is going on with his body. The fact that he recently found his body inexplicably altered suggests there is a lot they don't know. With friends like Tony Stark, Hank Pym, Hank McCoy, Reed Richards, etc, it would be possible for them to discover how the Super Soldier Serum works and any long term positive or negative affects. Cap can't take the risk of his body suddenly shutting down at any random moment. If it was possible he could lose his abilities in five years, a decade or whatever, that's something else he should make plans for. For the sake of the mantle of Captain America, the secrets to the Super Soldier Serum need to be unlocked so the heroes will know how long Captain America will be in the game.