Role of red blood cell distribution width (rdw) in thyroid dysfunction.

Authors:Geetha J P, Srikrishna R
Int J Biol Med Res. 2012; 3(2): 1476-1478  |  PDF File

Abstract

Background: Thyroid hormones play an important physiological role in humans. Erythrocyte abnormalities are frequently associated with thyroid dysfunction. However they are rarely investigated and related to the thyroid. Aim: In this study an attempt is made to evaluate Red blood cell distribution width (RDW) and Mean corpuscular volume (MCV) in patients with thyroid dysfunction.Methods: This is a prospective study. Based on Thyroid stimulating hormone (TSH) values it was categorized as Euthyroid with TSH value of 0.3-5.5. Hypothyroid when TSH value of >5.5. Hyperthyroid with TSH value of <0.3. Anemia was defined by hemoglobin level<13 g/dl in men and <12 g/dl in women, further classified as microcytic, normocytic, or macrocytic in the presence of MCV values of less than or equal to 80 fL, 80 to 100 fL, and greater than or equal to 100 fL, respectively. The normal reference range for RDW is 42.5±3.5 fl as SD. It indicates the measure of degree of anisocytosis. Venous blood samples are collected in the fasting state in these subjects. Serum separated and analyzed for thyroid status. EDTA samples were subjected for complete blood count using sysmex kx-21 analyzer. The significance of differences between groups was assessed by using multiple linear regression analysis. Results: The study included 273 subjects. There were 146 euthyroid, 85 hypothyroid and 42 hyperthyroid subjects. As compared with patients with euthyroid status for TSH values, RDW values significantly increased in both hypo and hyperthyroid patients. MCV values were significantly decreased in hyperthyroidism and significantly increased in hypothyroidism. Conclusion: In view of increased RDW in thyroid dysfunction, it suggests that abnormal levels of thyroid hormones might substantially influence the size variabitlity of circulating RBC’s. Their presence could steer towards subclinical thyroid dysfunction allowing its early management.