This is a flawed comparison because you do not need to "become a doctor" or read up on medical science to know that there is currently no way to get another pair of functioning human arms on top of the two you already have.

By the way, there are surgical options to grow taller by lengthening the limbs [1]. I'm not a doctor.

[1] http://abcnews.go.com/Health/york-man-grows-inches-surgery/s...