Objectives. The aim of the study was to investigate the relationship between serum thyrotropin (TSH) levels and performances on neuro-psychological tests of selected cognitive functions in patients with schizophrenia.
Method. Cognitive functions were assessed using the Trail Making Test (TMT, parts A & B), the Stroop Color-Word Interference Test, and the Verbal Fluency test. The TSH level was measured by means of the Architect TSH (Abbott Laboratories) - chemiluminescent microparticle enzyme immunoassay (CMIA) for the quantitative determination of serum TSH. Serum TSH was determined in 59 patients (26 women) diagnosed with schizophrenia, in most cases undifferentiated or paranoid. Cognitive functions were assessed in 29 patients from this sample (in that number in 17 women).
Results. In the group of 59 schizophrenic patients an elevated TSH level was found in a single case only, while in 11.9% of the participants TSH levels approximated the lower border of the normal range. The serum TSH level was negatively correlated with the performance time on the Stroop Test, part II. A significantly lower mean TSH level was found in the patients who scored on the TMT part B, below or on the border of the normal range, as compared to serum TSH of those whose performance was within the norm. In some of the patients with schizophrenia a tendency to lower TSH levels was noted.
Conclusions. Impairment of some cognitive functions was associated with lower TSH levels.