Cognitive and affective status in mild hypothyroidism and interactions with L-thyroxine treatment

While clinical hypothyroidism is associated with frank neuropsychological and affective alterations and is considered one of the causes of reversible dementia, the occurrence of these alterations and their treatment in mild hypothyroidism (MH) remains a controversial issue. Our aim was therefore to evaluate cognitive and psychological functions in a selected population of recently-diagnosed MH patients with minor subjective symptoms.

Thirty-six MH women (mean age 51.9 +/- 13.5 years) were observed after a careful assessment had excluded subjects with neurological, psychiatric and/or somatic disorders, or confounding conditions. The subjects were evaluated for thyroid function and tested with an extensive battery of neuropsychological tests and psychological rating scales, in basal conditions and after 6 months of L-thyroxine treatment.

Baseline neuropsychological performance was within the normal range, while an age-dependent reduction was found in attentive function. After L-thyroxine treatment, an increase in serum fT4 was detected in parallel with thyroid stimulating hormone (TSH) reduction. Verbal fluency and depression scores showed a slight improvement. A positive correlation was found between TSH reduction and improved mood scores.

From the analysis of the results, treatment of asymptomatic MH would seem advisable in order to re-set hormonal levels and, particularly in older subjects, to protect the brain against the potential risk of cognitive and affective dysfunctions.