Although a few early reports on the effects of GHRT in hypopituitary adults had already been published in the 1960s ( 2 ) and hypotheses had been made on the impact that GH might have in adults based on clinical studies in hypopituitarism ( 3 ), it was not until the availability of recombinant human GH that the research field of adult GHD was established. This evidence concerns the gene GH1 and hypopituitarism.