Changes of event related potential and cognitive processes in patients with subclinical hypothyroidism after thyroxine treatment.

Abstract Recently, it has been repeatedly shown that patients with subclinical hypothyroidism (SH) formerly considered as completely symptom free, may have numerous minimal, often non-specific subjective complaints, and that in those patients it is possible to prove many subtle but objective deviations. We decided to quantify whether there are event related potential (ERP) deviations as electrophysiological markers of cognitive activity in patients with SH and whether ERP could be influenced by thyroxine treatment leading to normalization of TSH level in serum. Event related potential (ERP) was examined in thirty one patients (mean age 52 +/- 12.5 years) with SH and without any other endocrine or metabolic diseases and in 29 subjects of the control group. From 31 patients 20 women (mean age 61.8 +/-6.8 years) were selected and divided into a group of 10 women treated six months with L-thyroxine until the normalization of TSH and remaining 10 women receiving placebo. ERP examination was repeated and all such patients also underwent neuropsychological examination consisting of the Wechsler Memory Scale and the MMPI/100 (Minnesota Multiphasic Personality Inventory). The interval between the diagnosis of SH and final evaluation of treatment was 16 months. In SH thyroxine treated patients the average P3 wave latency was 374 ms (SD 40.6), while in placebo group it was 340 ms (SD 32.3. P