GHRH-induced GH response in patients with senile dementia of the Alzheimer type.

To clarify the functional state of the somatotropinergic system at the hypothalamo-hypophyseal level in senile dementia of the Alzheimer type, the GHRH test was performed in three groups of subjects: a) healthy elderly subjects; b) early onset senile dementia patients; and c) late onset senile dementia patients. Intravenous administration of GHRH(1-44)NH2 (100 micrograms) elicited a marked plasma GH response with a maximum peak (709.54 +/- 259.0 pmol/l; P less than 0.005) 60 min after injection in patients with early onset senile dementia, but no significant response was detected in the other two groups. Electroencephalographic recording showed that GHRH modifies brain bioelectrical activity, decreasing frequency (0.52 +/- 0.15 Hz) and increasing amplitude (8.25 +/- 4.5 microV) of the electroencephalogram basic rhythm. The evaluation of mental performance and behaviour with a battery of different tests for mental assessment revealed that GHRH induces transient clinical changes in psychomotor behaviour. According to these results, it seems likely that the somatostatin deficiency reported in senile dementia of the Alzheimer type may account for the enhanced GHRH-induced GH response observed in patients with early onset senile dementia. In consequence, the GHRH test might constitute a useful antemortem marker for senile dementia of the Alzheimer type if the present results can be replicated in early stages of the disease.