The TRH stimulation test in Alzheimer's disease and major depression: Relationship to clinical and CSF measures

Abstract

A blunted thyroid-stimulating hormone (TSH) response to exogenous thyrotropin-releasing hormone (TRH) has been reported to occur consistently in patients with major depression and less consistently in patients with Alzheimer's disease (AD). In this study we compared the TSH response to TRH in a large group (n = 40) of AD patients, elderly patients with major depression (n = 17), and age-matched controls (n = 14) to further characterize how it may relate to clinical variables, baseline thyroid function tests, and cerebrospinal fluid measures. Comparisons of TRH stimulation test response across all three groups revealed that patients with major depression had lower stimulated TSH levels (ΔmaxTSH) (p < 0.02) and higher (though still within normal limits) mean thyroxine (T 4) levels (p < 0.05) than the AD patients or controls. AD patients with a blunted TSH response had a significantly higher mean free T 4 (FT 4) level (p < 0.03) and tended to be more severely demented (p < 0.01) than those with a nonblunted response.