A Pilot Study on the Relationship Between Thyroid Status and Neuropsychiatric Symptoms in Patients with Alzheimer Disease

Background: Growing evidence links alternation of the thyroid function to the pathogenesis and progression of Alzheimer disease (AD). However, only a few studies evaluate the association between thyroid hormone levels and neuropsychiatric manifestations in patients with AD. This study aimed to investigate the relationship of thyroid hormone levels and neuropsychiatric symptoms in euthyroid patients with AD.

Methods: Forty patients with AD (26 women and 14 men), with no prior AD treatment within 4 weeks before study entry, were evaluated on their thyroid status (total triiodothyronine (TT3), total thyroxine (TT4), and thyroid-stimulating hormone (TSH)), cognition (Mini-Mental State Examination (MMSE) and Alzheimer's disease Assessment Scale-Cognitive Subscale (ADAS-cog)), neuropsychiatric symptoms (Neuropsychiatric Inventory (NPI)) and depression (Hamilton Rating Scale for Depression (HAMD(17))). The unique relationship between thyroid hormones and cognitive function and mood was examined with multivariate linear regression analyses. The thyroid status between the neuropsychiatric symptoms group and the non-neuropsychiatric symptoms group was examined with independent-samples t-test.

Results: In euthyroid AD patients with agitation and irritability has lower TSH serum level than those without these symptoms (t = -2.130, P < 0.05; t = -2.657, P < 0.05); and core score of HAMD is significantly associated with the serum level of TSH (β = 0.395, P < 0.01). There is no significant association between thyroid hormone levels and cognition (MMSE, ADAS-cog and its subscale score).

Conclusion: There might be a relationship between thyroid hormone levels and the neuropsychiatric symptoms in euthyroid patients with AD.