Effect of Levothyroxine on Spatial Working Memory Impairments in Patients with Subclinical Hypothyroidism:Functional MRI Observation / 中国医学影像学杂志

ABSTRACT

Purpose To explore the effect of Levothyroxine on spatial working memory in patients with subclinical hypothyroidism (SCH) using blood oxygenation level dependent-functional MRI (BOLD-fMRI). Materials and Methods Sixteen patients with SCH before and after 6 months levothyroxine (LT4) treatment and 16 matched euthyroid volunteers underwent n-back task fMRI scanning. AFNI software was used for localization and quantification. Results All the subjects demonstrated activated areas including bilateral dorsolateral prefrontal cortex (DLPFC), bilateral premotor area (PreMA), supplementary motor area/anterior cingulate cortex, bilateral parietal area (PA) and right caudate nucleus/thalamus, with right hemisphere dominance. Quantitative analysis of regions of interests showed that all these regions had load effect related to memory load in the control group (P<0.001), whereas only left DLPFC, left PA, bilateral PreMA and right caudate nucleus/thalamus showed the same effect in SCH group. After 6-month treatment with LT4, BOLD signal change was observed in SCH patients within the right DLPFC, right PA and anterior cingulate/supplementary motor cortex (P<0.001). The activation intensity of working memory related brain regions was lower in SCH group compared with that of the control group. Conclusion Spatial working memory impairments in SCH patients are likely related to decreased right DLPFC and right posterior parietal function. LT4 replacement therapy is important to improve and reverse the memory impairment.