DOI: 10.5937/pramed1502097D PROFESSIONAL ARTICLES P300 EVENT RELATED POTENTIAL APPLICATION TO COGNITIVE STATUS ASSESSMENT OF THE PATIENTS WITH SUBCLINICAL HYPOTHYROIDISM AUTHORS Dejanović M. 1 , Ivetić V. 2 , Nestorović V. 1 , Milanović Z. 1 , Biševac B. 1 , Miletić M. 1 , Mirić M. 1 CORRESPONDENT MIRJANA DEJANOVIĆ Medicinski fakultet, Univerzitet u Prištini, Kosovska Mitrovica, Srbija mirjana.dejanovic@gmail.com 1 Department of Physiology, Faculty of Medicine, University of Priština, Kosovska Mitrovica, Serbia 2 Department of Physiology, Faculty of Medicine, University of Novi Sad, Novi Sad, Serbia SUMMARY Disturbances of thyroid function are often accompanied by cognitive and affective disorders. Assessment of cog- nitive status in the patients with subclinical hypothyroidism represents a possibility for early diagnostics of cognitive impairment and timely introduction of necessary pharmacotherapy treatment. The aim of this study was to quantify whether there are P3 event related potential (ERP) deviations as electrophysiological markers of cognitive activity in patients with subclinical hypothyroidism. P300 potentials were examined in thirty patients with subclinical hypothy- roidism and in 30 healthy subjects of the control group. P300 was recorded using the classic auditory oddball para- digm, with 20% of target and 80% of non-target stimuli. The results analysis showed a significantly longer latency P300 and reduced amplitude P300 in subjects with subclinical hypothyroidism compared to euthyroid subjects. There is also a statistically significant negative correlation between the results of a mini mental state examination and the P300 la- tency at Fz electrode (r= -0.47, p <0.01) and Cz electrode (r= -0.43, p =0.017). P300 ERP is important in the evalua- tion of patients with subclinical hypothyroidism, due to the sensitivity in the detection cognitive disorders. Key words: P300, hypothyroidism INTRODUCTION It is known that thyroid hormones are important for normal brain function [1,2]. Disturbances of thyroid func- tion are often accompanied by cognitive and affective disorders. Of particular importance is the diagnosis of cognitive disorders, which are, however, often over- looked, and closely connected with the quality of life of patients. Clinically manifest hypothyroidism can lead to changes in many cognitive domains, including attention, concentration, memory, executive function, and impact of subclinical hypothyroidism on cognitive function is still unclear [3]. Subclinical hypothyroidism may have similar, but more subtle effects on cognitive functions. Subclinical hypothyroidism, defined as an asympto- matic state with elevated serum thyroid stimulating hormone (TSH) levels while the values of free and total tyroxin (T4) are normal [4]. There is no consensus in the literature whether the subclinical hypothyroidism may induce change of the cognitive functions. Some authors argue that the mild subclinical hypothyroidism (average TSH concentration less than 10mU/L) may induce cogni- tive and affective disorders which can be corrected by the tyroxin substitution [5]. There are increasingly more evidence of a disturbance of cognitive function under subclinical hypothyroidism. Many authors believe that the decline in cognitive function may vary depending on the concentration of thyroxine. Volpato followed the values of thyroxine and TSH in women with normal thyroid function for a period of three years and found that cognitive decline was faster among women with lower concentrations of thyroxine, although all were within the normal range [6]. Samuels et al. find weaker health status, cognitive dysfunction, impaired working memory, and motor learning in patients treated with thyroxine compared to 20 euthyroid persons aged 20-45 years, with TSH within the reference values [7]. Testing of thyroid function is an integral part of the di- agnostic protocol for dementia [8]. On the other hand, some studies did not find a link between subclinical hy- pothyroidism and cognitive and affective disorders [9, 10]. There is not enough evidence that treating hypothy- roidism recovers cognitive functions [11, 12, 13]. In clinical practice, for assessing and monitoring cognitive deficits, neuropsychological tests are usually used. However, the tests require the cooperation of pa- tients and are often very complicated and exhausting. For these reasons, special interest piqued to learn that the recently introduced new neurophysiological methods in the study of cognitive processes in healthy subjects and in clinical practice- event-related potentials as an objective neurophysiological methods can contribute to the early diagnosis of cognitive impairment. In the last 20 years P3 cognitive potentials research is very intense and clearly indicate that this component can serve as an indicator of cognitive function. In this regard, it is quite 97