The value of P300 event related potentials in the assessment of cognitive function in subclinical hypothyroidism.
BACKGROUND
Mild hypothyroidism (thyroid stimulating hormone [TSH] less than 10 mIU/L) induces reversible cognitive dysfunction, which can be evaluated by event related potentials (ERP). So far, only little is known about the impact of subclinical hypothyroidism on ERP as electrophysiological markers of cognitive activity. The aim of this study was to follow-up P300 latencies and amplitudes in patients with subclinical hypothyroidism and to evaluate the influence of thyroxine treatment which led to the normalization of TSH level in serum.


METHODS
We recorded the P300 wave using an auditory oddball paradigm in 60 patients (mean age 51.1±6.2 years, range 40-62 years), with subclinical hypothyroidism (normal mean value of FT4, with elevated TSH levels) at baseline, after 3 months, after 6 months and in 30 healthy control subjects. 30 patients treated six months with L-thyroxine until the normalization of TSH and 30 patients received placebo.


RESULTS
The P300 latencies in patients with subclinical hypothyroidism were significantly longer, and the P300 amplitudes were significantly smaller than those of the control group. In the thyroxine treated patients P300 latency continuously decreased over the observation period with a significant difference after 6 months compared to baseline (P<0.01). The amplitude P300 showed no significant changes over time.


CONCLUSIONS
Our results show the importance of P300 event related potentials in the detection of cognitive changes in patients with hypothyroidism. The P300 latency stands out as a marker for cognitive function recovery during treatment with thyroxine.
Department of Physiology, Faculty of Medicine, University of Priština, Kosovska Mitrovica, Serbia - mirjana.dejanovic@gmail.com.
Mirjana
M
Dejanović
Laboratory of Neurophysiology, Department of Physiology, Faculty of Medicine, University of Novi Sad, Novi Sad, Serbia.
Vesna
V
Ivetić
Department of Physiology, Faculty of Medicine, University of Priština, Kosovska Mitrovica, Serbia.
Vojkan
V
Nestorović
Department of Physiology, Faculty of Medicine, University of Priština, Kosovska Mitrovica, Serbia.
Zvezdan
Z
Milanović
Department of Anatomy, Faculty of Medicine, University of Novi Sad, Novi Sad, Serbia.
Mirela
M
Erić
D000328:Adult; D003072:Cognition Disorders / Q000175:diagnosis* / Q000209:etiology* / Q000523:psychology; D018913:Event-Related Potentials, P300; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000150:complications* / Q000188:drug therapy / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D020127:Recovery of Function; D013974:Thyroxine / Q000627:therapeutic use
D013974:Thyroxine