Hypothalamic-pituitary-thyroid axis in patients with Alzheimer disease (AD).

Objective: We observed the function of hypothalamic-pituitary-thyroid axis in patients with Alzheimer disease (AD) using a case-control study.

Methods: The case was a cohort that included 50 patients with AD. For each case subject, 1 control who was of similar age, sex, daily activities (scale of Lawton), sleep quality (Pittsburgh Sleep Quality Index), and depression (15-item Geriatrics Depression Scale) was recruited. Thyrotropin-releasing hormone (TRH), thyroid-stimulating hormone (TSH), total triiodothyronine (TT3), total tetraiodothyronine (TT4), free triiodothyronine (FT3), and free tetraiodothyronine (FT4) were detected using radioimmunity.

Results: Compared with the healthy controls, the patients with AD had significantly lower levels of TRH (67.72 ± 18.44 vs 78.64 ± 14.31 pmol/L; t = 2.078; P = 0.036), TSH (3.89 ± 1.22 vs 4.31 ± 1.07 mIU/L; t = 2.331; P = 0.024), TT3 (1.44 ± 0.21 vs 1.63 ± 0.19 nmol/L; t = 3.761; P = 0.018), TT4 (119.71 ± 18.64 nmol/L vs 129.54 ± 23.17 nmol/L; t = 1.328; P = 0.044), FT3 (4.01 ± 1.27 vs 5.41 ± 0.99 pmol/L; t = 4.976; P = 0.008), and FT4 (9.84 ± 1.56 vs 12.96 ± 2.20 pmol/L; t = 5.381; P = 0.006). In the AD cases, none of the correlations between TRH and TSH, TT3, TT4, FT3, and FT4, and between TSH and TT3, TT4, FT3, FT4 was significant. However, in the healthy controls, TRH was significantly correlated with TSH (R = 0.020; P = 0.042) and FT4 (R = 0.015; P = 0.018), and TSH was significantly correlated with TT4 (R = 0.209; P = 0.017) and FT4 (R = 0.215; P = 0.009).

Conclusion: Alzheimer disease was associated with abnormal function of the hypothalamic-pituitary-thyroid axis.