Address for correspondence: Baris Akinci, Division of Endocrinology of Metabolism, Department of Internal Medicine, University of Dokuz Eylul, Inciralti, Izmir, Turkey 35340, Τel.: +90-232-4123744, Fax: +90-232-2792267, e-mail: baris.akinci@deu.edu.tr Received 07-05-07, Revised 20-08-07, Accepted 20-09-07 The alteration of serum soluble CD40 ligand levels in overt and subclinical hypothyroidism Baris Akinci, 1 Abdurrahman Comlekci, 1 Serkan Yener, 1 Tevfik Demir, 1 Firat Bayraktar, 1 Faize Yuksel, 2 Sena Yesil 1 1 Division of Endocrinology and Metabolism, 2 Division of Haematology, Dokuz Eylul University Medical School, Department of Internal Medicine, Izmir, Turkey AbstrAct ObJEctIVE: there is controversy as to whether hypothyroidism increases cardiovascular risk. the effect of levothyroxine on the cardiovascular risk profile is also unclear. recent studies suggest that there is evidence of inflammation and endothelial dysfunction in hypothyroidism. soluble cD40 ligand (scD40L) is a protein expressed mainly by activated platelets which have been found to be associated with cardiovascular events. the aim of our study was to in- vestigate serum scD40L levels and the effect of levothyroxine replacement on scD40L levels in overt and subclinical hypothyroidism. DEsIGN: We assessed lipid profile, serum scD40L and hscrP levels in 21 overt and 22 subclinical hypothyroid age-matched female patients with chronic autoimmune thyroiditis at baseline and one month after achieving euthyroidism by levothyroxine replacement, and compared them with the data from 22, age-matched, healthy controls. rEsuLts: Overt and subclinical hypothyroid patients had decreased scD40L levels compared to age-matched controls. the patients with subclinical hypothyroidism had slightly increased hscrP levels, but the result was not statistically significant. In multiple regres- sion analysis, Ft3 and Ft4 were found to be independent predictors of scD40L levels. After levothyroxine replacement, serum scD40L levels increased significantly in the patients with overt hypothyroidism. Although an increase was also observed in the subclinical hypothyroid group, it was not statistically significant. Levothyroxine replacement had no significant effect on hscrP levels in the patients with overt hypothyroidism. However, the subjects with sub- clinical hypothyroidism showed a significant reduction in hscrP levels after levothyroxine. cONcLusION: the values of scD40L and hscrP in our study suggest that inflammatory pathways are complex and may be affected by different factors in hypothyroidism. Key words: Cardiovascular risk, CD40, Inflammation, Levothyroxine, Thyroid dysfunction Research paper HORMONES 2007, 6(4):327-333