Pegvisomant is a GH analogue that includes a single amino acid substitution at position 120 that generates the GHR antagonist. Additional changes include amino acid substitutions within binding site 1 and a further modification by the addition of polyethylene glycol moieties that increase the half-life and reduce the immunogenicity of the molecule. In acromegalics, pegvisomant is the most effective treatment for normalizing the IGF-I, and pegvisomant significantly improves insulin sensitivity in patients suffering from acromegaly. However, there are simply no data available that might support a role for pegvisomant treatment in disorders in which glucose metabolism is disturbed and in which reducing GH action would be theoretically beneficial.