Subclinical hyperthyroidism in dementia and correlation of the metabolic index in FDG-PET

Thyroid hormone status and thyroid antibodies were evaluated in patients suffering from dementia for further study of an association of hyperthyroidism with AD and vascular dementia (VD), respectively.

In 77 patients with dementia, and 42 controls, thyrotropin (TSH) and thyroid antibodies were correlated with the different types of dementia and the metabolic index (MI) based on imaging with F-18-2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET).

Twenty-two of all patients with dementia (29%) had borderline (TSH 0.3-0.5 mU/l) or decreased TSH levels (TSH < 0.3 mU/L). TSH values were significantly lower in patients suffering from AD (median: 1.1 mU/l) and VD (0.5 mU/l) than in the control group (1.5 mU/l) (p < 0.01). Decreased or borderline TSH levels were present in 52% of the patients with VD, but in only 10% of the controls, and in 23% of the patients with AD. Antibodies to thyroid peroxidase were positive in 16% of all patients with dementia. The MI in patients suffering from AD with borderline TSH levels was 0.81 (0.70, 0.94). In contrast, patients suffering from AD with normal TSH values showed a slightly higher MI of 0.84 (0.76, 0.89) (p = n.s.).

Decreased or borderline TSH values are associated with an increased probability of having dementia, especially VD.