This study was undertaken to assess the value of growth hormone (GH) response to clonidine as a tool in the differential diagnosis between depression and dementia. This response is known to be blunted in depression, and neurochemical changes observed in senile dementia of the Alzheimer type (SDAT) could lead to an up-regulation of GH secretion. No difference was observed between GH response in depressed and demented patients. Together with studies on GH basal secretion in Alzheimer's disease, this finding suggests that the final consequence of SDAT-related changes in an accentuation of the effects of aging on GH reactivity.