Characteristic plasma hormone changes in Alzheimer's disease.

A systematic endocrine investigation in dementia, depression and control subjects showed that plasma growth hormone (GH) was higher in the morning and plasma TSH concentrations were higher throughout the day in Alzheimer-type dementia (ATD) than in age-matched depressed patients (MDD), and plasma TSH concentrations were also higher throughout the day in female ATD compared with age-matched female control subjects. The increased plasma TSH concentrations could not be due to reduced negative feedback because plasma T3, T4 and rT3 were in the normal range. Plasma concentrations of oestrogen-stimulated neurophysin (ESN) were lower throughout the day in ATD compared with MDD and controls and lower in the morning compared with other dementias. The high plasma GH and TSH concentrations in ATD may reflect the reduced hypothalamic content of somatostatin in ATD, and the reduced concentrations of ESN may reflect reduced cholinergic activity in ATD brain. These selective hormonal changes provide a useful diagnostic test for Alzheimer's disease.