Effects of repetitive transcranial magnetic stimulation on cognitive function and hormone levels in early stroke patients with low thyroid hormone levels

Background: This study aimed to observe the effects of repetitive transcranial magnetic stimulation (rTMS) on cognitive function and thyroid hormone levels in early older stroke patients with low thyroid hormone levels, and to investigate the correlation between the changes in thyroid hormone levels and the improvements in cognitive function after stroke.

Methods: Forty older stroke patients who met the inclusion criteria were recruited and randomized into a magnetic-stimulation group (rTMS group) and a sham-stimulation group (Sham group). The rTMS group received low-frequency true stimulation and the Sham group received low-frequency sham stimulation. Patients' cognitive scores, activity of daily living(ADL) scores, and their levels of triiodothyronine (T3), free triiodothyronine (FT3), thyroxin (T4), free thyroxine (FT4), and thyroid stimulating hormone (TSH) were assessed before the intervention, after the 4-week intervention, and after an additional 4 weeks of follow-up; Repeated measurement analysis of variance was used to compare the changes of each index in the two groups at different times and the correlations between patiens' cognitive function scores and their changing hormone levels were subsequently investigated.

Results: Thirty-one patients were included in this study: 16 patients in rTMS group and 15 patients in the Sham group. Repeated-measures ANOVA showed that patients' T3,FT3 and TSH levels tended to increase at 4-week intervention and at the follow up (p < 0.05), and that the rTMS group had a better effect on improving T3 than the Sham group (F_group = 5.319, p = 0.028); The cognitive scale at different time points in both groups showed an upward trend (p < 0.05), and the MoCA, DSF, DSB scores in the rTMS group were statistically higher than those in the Sham group at the end of the 4-week intervention and at the follow-up (p < 0.05); The changes in the levels of T3 before and after 4-week intervention were positively correlated with the changes in the MoCA scores (r = 0.638, p < 0.05). And the difference in T3 level change was positively correlated with the difference in delayed recall, attention and naming score change (r = 0.562, p < 0.05; r = 0.562, p < 0.05; r = 0.531, p < 0.05); and the difference in FT3 level change was positively correlated with the visuospatial and executive function (r = 0.514, p < 0.05).

Conclusion: Repetitive transcranial magnetic stimulation improved cognitive function and elevated T3 levels in older patients with post-stroke cognitive dysfunction who had low thyroid hormone levels. Within the normal range, increases in T3 levels are positively correlated with changes in cognitive function.