Objective: Moderate and severe primary adult hypothyroidism produces cognitive and behavioral disturbances, but the effects of mild hypothyroidism are not well established. We have tried to determine the pattern of cognitive performance and the effect of hormonal treatment in mild hypothyroidism.
Patients and methods: 15 patients with subclinical or very mild hypothyroidism were compared with other 15 patients suffering from mild diseases without central nervous system damage, who were matched in age, sex and previous intelligence. A neuropsychological battery, including tests of global cognitive performance (Mini Mental Status Examination, WAIS), attention (reaction time), visual memory (Benton test, Rey's Figure), verbal memory (word learning), verbal fluency and executive functions (Trail Making Test), was applied.
Results: Hypothyroid patients had worse performance in some WAIS subtests, reaction time, verbal fluency, free recall and copy of the Rey's figure. After hormonal treatment, a significant improvement and normal performance in almost all cognitive functions were found.
Conclusions: Even mild hypothyroidism produces cognitive defects, mainly in tasks with high attentional requirements, that can and should be corrected with hormonal replacement.