That is not how the natural law tradition usually sees things. For example, that homosexuals suffer immediate suffering from not being able to enter into and consummate relationships, which may affect their psychological and spiritual well-being, but it is still held that homosexual acts are immoral.
I think part of the answer is that we are bodies as well as souls, and should be whole as far as possible. Our biological functions and ends are meant to support our higher ends, and we should, if rational, respect the proper ends of our biology. A limb or organ that is going to kill us has ceased to perform its function and end, so it is permissible to remove it, but one that is still functioning well should not be a remove, as this frustrates it end. I do not know where the line is drawn though, about organs that are sick but still functioning to a degree. Perhaps there is no hard and fast rule.