Abstract: The present invention relates generally to a method for the treatment and/or prophylaxis of conditions arising from or otherwise associated with aberrations in hormone signalling. The present invention further provides an animal model useful for screening for agents capable of agonizing or antagonizing hormone signalling. More particularly, the present invention contemplates a method for the treatment and/or prophylaxis of conditions arising from or otherwise associated with aberrations in growth hormone signalling. The present invention further comprises a genetically modified animal. More particularly, the animals are genetically modified such that they have altered growth hormone signalling. The genetically modified animals of the present invention range from laboratory animals useful inter alia for animal models for studying hormone regulation and for the development of therapeutic protocols predicated, in part, on modulating hormone signalling to livestock animals.