The relationship between brain neurotrophic factors and thyroi̇d function, vitamin B12, folic acid in mood disorders

Objective: Mood disorders is a chronic disease which severely disrupt the functionality. Its etiology is still unknown. But neurotrophic factors, thyroid abnormalities, deficiency of vitamin B12 and folic acid play the role in the etiology. The aim of this study is to examine the relationship between BDNF, GDNF and TSH, fT3, fT4, vitamin B12 and folic acid in patients with mood disorders. Method: One hundred and forty-five patients (thirty-seven euthymic, forty-one manic, twenty-nine bipolar depression, thirty-eight unipolar depression) and sixty-seven healthy controls were enrolled in the study. Serum BDNF and GDNF levels were measured using a sandwich-ELISA kit, TSH, fT3, fT4 levels were measured with chemiluminescent method and vitamin B12, folic acid levels were measured with Cemiluminesans Microparticle Immunoassay (CMIA) method. Patients were evaluated with Structured Clinical Interview for DSM-IV-TR (SCID-I), Young Mania Rating Scale (YMRS), Hamilton Depression Ratig Scale-17 (HAMD), Clinical Global Impression Scale (CGI) and Global Assessment of Functioning Scale (GAF)., Kruskall Wallis, Mann Whitney U, chi-square, Spearman correlation analysis were used for statistical analysis by SPSS15.0 programme. Results: Serum BDNF levels were lower in bipolar disorder episodes (manic or depressive episodes), and unipolar disorders than healthy volunteers and correlated with episode severities. GDNF levels were not different. fT3 levels were lower in manic, depressive and even euthymic episodes, and unipolar depression than healthy controls. fT4, vitamine B12 and folic acid did not differ among the groups. There was a positive correlation between BDNF and fT4 in bipolar depression, a negative correlation between GDNF and fT4 in unipolar depression. Conclusion: Our findings support the concept of decreased BDNF levels as a state-marker in mood episodes. fT4 was shown to contribute to the pathophysiology in depressive episodes, by acting parallel to BDNF and opposite to GDNF levels. Key words: Mood disorders, BDNF, GDNF, thyroid functions, vitamin B12, folic acid