TRH stimulation test in dementia of the Alzheimer type and elderly controls.

Dementia of the Alzheimer type (DAT) is known to be a heterogeneous syndrome with many clinical manifestations, including depression. In the present study, the thyrotropin-releasing hormone (TRH) stimulation test, previously used as a possible biological marker of depression, was administered to 15 DAT patients and 10 elderly controls. Seven out of 15 (47%) of the patients but none of the controls showed a blunted response with maximal changes of thyroid-stimulating hormone (TSH) from baseline of less than or equal to 7 microIU/ml following injection of 500 micrograms of TRH. The degree of blunting did not correlate with concurrent depression ratings.