In Chapter one I have reviewed the origins of thinking concerning growth hormone and how clinicians like Pierre Mariw, Minkowski and Cushing carefully related clinical conditions to pathology and came to hallowed conclusions regarding growth hormone. The catastrophe of the appearance of Jacob-Creutzfeldt disease in some patients who had received cadaveric growth hormone was subsequently avoided by the early synthesis of purified growth hormone by DNA recombinant techniques which has led to the current use of growth hormone indistinguishable in structure and physiological action from the naturally occurring hormone. However since the naturally occurring hormone was really never extracted in a 100% pure form who then can tell what are all its physiological actions?