Knowledge of the interaction between growth hormone (GH) and the growth hor
mone receptor (GHR) has led to the rational design of a GHR antagonist. An
analogue of GH able to block the action of GH at the cellular level offers
greater specificity of effect compared with current medical therapies and i
s not dependent on tumour characteristics. This chapter reviews the interac
tion between GH and the GHR, and discusses the outstanding issues regarding
GHR antagonist therapy in acromegaly.