We studied the growth hormone (GH) response to GH-releasing hormone (GHRH) and the thyroid-stimulating hormone (TSH) response to thyrotropin-releasing hormone (TRH) in four groups of patients with dementia and examined whether GH and TSH secretion is altered in patients with Alzheimer's disease. The four groups included those with Alzheimer's disease (n = 28), parkinsonism with dementia (n = 10), progressive supranuclear palsy with dementia (n = 10), and dementia of vascular origin (n = 28). The results showed no differences among the four groups in GH response to GHRH (12.2 +/- 2, 10.7 +/- 2, 8.9 +/- 1.1, and 9.9 +/- 1.9 micrograms/ml, respectively); there was no correlation between GH response to GHRH and sex, stage of the disease, or cerebral atrophy. The proportion of patients with exaggerated, normal, or lower GH response was similar in the four groups in terms of TSH response to TRH (9.2 +/- 0.9, 11.1 +/- 1, 11.1 +/- 1, and 10.3 +/- 1 mU/ml, respectively), nor was there a correlation between TSH response to TRH and sex, stage of the disease, cerebral atrophy, or GH response to GHRH. The proportion of those with exaggerated, normal, or lower TSH response was similar in the four groups. Cerebrospinal somatostatin levels were similar in Alzheimer's disease and vascular dementia patients. These findings indicate that neither GH response to GHRH nor TSH response to TRH provides a useful diagnostic adjunct in Alzheimer's disease patients.