Introduction. Pathologic prevalence of dementia increases worldwide, it already involves up to 50 million people. The premier reason of it still is the Alzheimer's disease. Global prevalence of Hashimoto's chronic autoimmune thyroiditis also progresses rapidly, making it most highly spread autoimmune disorder of nowadays. Earlier several researchers came to conclusion that both hyperthyroidism and hypothyroidism may be related to higher risk of Alzheimer's disease [1]. We demonstrated that microglial phagocytic activity in CNS is controlled by thyroid hormones [2], as well as many metabolic and morphogenetic processes in brain.
Aims. To explore probable relationships between Hashimoto's thyroiditis and Alzheimer's disease checking early extracerebral expression of Alzheimer's marker among patients with Hashimoto's disease, but without any Alzheimer's clinical signs.
Material and methods. We took a scraping of buccal epithelium (BE) for the detection of pre-clinical marker of Alzheimer's disease - the Tau protein (TP). By special technic [3] the immunofluorescence analysis of samples was performed with confocal microscope 1000B (Japan), the data obtained were processed via ImageJ program. The main group of patients included 7 persons (6 females) without any clinical signs of Alzheimer's disease, but with diagnosis of Hashimoto thyroiditis, established according modified criteria of Japanese Thyroidological Association [4] and being under treatment with “Euthyrox©” (L- thyroxine) or “Thyrozol©” aged from 8 to 77 years old. Control group included 8 apparently healthy persons (7 females) aged from 10 to 75. Also we compared dental status of control and main groups, using conventional dental indexes and scales of cavities and periodontitis. Thyroid hormones, thyrotropin and anti-thyroid antibodies level in blood was measured by ELISA.
Results. TP expression was verified in BE in 100% of Hashimoto's thyroiditis patients [average level of expression was 17,51 conventional units (CU)], while in control group the test was negative with the average level of expression 0,35 CU (p < 0.001 with main group). No difference between groups in dental status was revealed, which rules out possible local reasons for their difference in TP expression. TP expression level did not correlate to age or sex of patients, neither to their blood level of thyroid hormones.
Conclusion. There is a relation between preclinical expression of TP and Hashimoto's thyroiditis. The buccal expression of TP precourses the first clinical manifestations of Alzheimer's disease.
Acknowledgement. Supported by the grant of the RF Government 14.W03.31.0009, project 15.34.3.2017.
