Purpose This study uses the diffusion tensor imaging to explore diffusion metrics changes of corpus callosum subregion,and to further analyze the relationship among these changes and the cognitive and emotional in adults with primary hypothyroidism.Materials and Methods From October 2019 to September 2021,32 hypothyroidism patients were recruited from Gansu Provincial Hospital,whereas 33 healthy controls were recruited through advertisements.The comprehensive thyroid-related hormone levels tests,as well as neurocognitive/neuropsychiatric assessment and diffusion tensor imaging data of all participants were carried out.The differences in corpus callosum subgroups of diffusion metrics between the two groups were recorded and compared,the partial relationships between these diffusion metrics and thyroid-related hormone levels and neurocognitive/neuropsychiatric function were analyzed and measured.Receiver operating characteristic curves were constructed to evaluate the diagnostic performance.Results Lower fraction anisotropy,higher mean diffusivity and radial diffusivity in genu and body of the corpus callosum and higher axial diffusivity in genu of the corpus callosum were found in hypothyroidism compared with healthy controls(P<0.01).These diffusion metrics were negatively correlated with cognition and emotion(r=-0.448-0.440,P=0.010-0.043),and the fraction anisotropy value in genu of the corpus callosum had the largest area under the curve(0.777).Conclusion Hypothyroidism patients show widespread microstructural changes within the genu and body of the corpus callosum,which,respectively,associated with cognition and emotion.This study provides a new perspective to further understanding the pathophysiology of the cerebral impairment in hypothyroidism.