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Arquivos Brasileiros de Endocrinologia & Metabologia

On-line version ISSN 1677-9487

Arq Bras Endocrinol Metab vol.58 no.9 São Paulo Dec. 2014 

Cartas ao Editor

Red cell distribution width in subclinical hypothyroidism

Distribuição dos glóbulos vermelhos ampliada no hipotiroidismo subclínico

Sevket Balta 1  

Mustafa Aparci 2  

Cengiz Ozturk 3  

Sait Demirkol 3  

Turgay Celik 3  

Atila Iyisoy 3  

1Department of Cardiology, Eskişehir Military Hospital, Eskişehir, Turkey

2Department of Cardiology, Etimesgut Military Hospital, Ankara, Turkey

3Department of Cardiology, Gulhane Medical Academy, Ankara, Turkey

We have read the article “The value of red blood cell distribution width (RDW) in subclinical hypothyroidism” by Hea Min Yu and cols. (1). They aimed to investigate the relationship between the subclinical hypothyroidism and RDW levels in a healthy population. They concluded that RDW levels were correlated with euthyroid and subclinical thyroid status.

This study gives important information on this clinically relevant condition. Thanks to the authors for their contribution. We think that some points should be discussed. Some markers have been found to be associated with early and late complications in many conditions. Inflammatory cytokines, high-sensitivity C-reactive protein (CRP), natriuretic peptides, neurohormones have recently established to be useful markers for diagnosis and prognosis in many diseases. However, these markers are very expensive and are not easily used in clinical practice. Elevated RDW is a measure of the variability in size of circulating erythrocytes and is expressed as the coefficient of variation of the erythrocyte volume. As several routine haematology instruments can analyse erythrocyte volume, RDW is available in most clinical settings. The ready availability of this parameter without additional cost may encourage its wider use in clinical practice.

Several studies have reported that elevated RDW levels are associated with poor prognosis in the setting of atherosclerosis, heart failure, stroke, peripheral arterial disease, older age (2). However, RDW may also reflect ethnicity, neurohumoral activation, renal dysfunction, hepatic dysfunction, nutritional deficiencies (i.e. iron, vitamin B12, and folic acid), bone marrow dysfunction, inflammatory diseases, chronic or acute systemic inflammation (3) and use of some medications like antihypertensive therapy (4).

In addition, the authors used the formula developed and validated in the Modification of Diet in Renal Disease (MDRD) to estimate glomerular filtration rate (GFR). However, MDRD formula might measure higher GFR in younger age groups and lower GFR in older individuals compared to the Cockcroft-Gault equation (5). Although the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) recently published an equation for GFR estimate using the same variables (serum creatinine level, age, sex, and race) as the MDRD formula, the CKD-EPI equation more accurately categorized the individuals with respect to long-term clinical risk compared with the MDRD formula (6).

As a conclusion, we strongly believe that the findings obtained from the current study will lead to further studies examining the relationship between inflammation and subclinical hypothyroidism (7). Not only RDW but also mean platelet volume, neutrophil lymphocyte ratio, CRP and uric acid are easy methods to evaluate the inflammation in patients with subclinical hypothyroidism (8). These markers might be useful in clinical practice (9). Finally, it would be better if the authors might define how much time between blood collection and arrival to the laboratory they specified on measuring RDW levels, because of the delaying blood sampling can cause abnormal results in RDW measurements.


Yu HM, Park KS, Lee JM. The value of red blood cell distribution width in subclinical hypothyroidism. Arq Bras Endocrinol Metabol. 2014;58(1):30-6. [ Links ]

Balta S, Demirkol S, Aydogan M, Unlu M. Red cell distribution width is a predictor of mortality in patients undergoing coronary artery bypass surgery. Eur J Cardiothorac Surg. 2013 Feb 21; Epub ahead of print. [ Links ]

Balta S, Demirkol S, Hatipoglu M, Ardic S, Arslan Z, Celik T. Red cell distribution width is a predictor of mortality in patients with severe sepsis and septic shock. Am J Emerg Med. 2013 Apr 12. [ Links ]

Fici F, Celik T, Balta S, Iyisoy A, Unlu M, Demitkol S, et al. Comparative effects of nebivolol and metoprolol on red cell distribution width and neutrophil/lymphocyte ratio in patients with newly diagnosed essential hypertension. J Cardiovasc Pharmacol. 2013;62(4):388-93. [ Links ]

Herzog CA. Kidney disease in cardiology. Nephrol Dial Transplant. 2009;24(1):34-7. [ Links ]

Matsushita K, Selvin E, Bash LD, Astor BC, Coresh J. Risk implications of the new CKD Epidemiology Collaboration (CKD-EPI) equation compared with the MDRD Study equation for estimated GFR: the Atherosclerosis Risk in Communities (ARIC) Study. Am J Kidney Dis. 2010;55(4):648-59. [ Links ]

Demirkol S, Balta S, Dinc M, Ay SA, Kucuk U, Unlu M. Arterial stiffness should be evaluated with other inflammatory markers in patients with subclinical hypothyroidism. Arq Bras Endocrinol Metabol. 2013;57(9):754-5. [ Links ]

Demirkol S, Balta S, Unlu M, Yuksel UC, Celik T, Arslan Z, et al. Evaluation of the mean platelet volume in patients with cardiac syndrome X. Clinics (Sao Paulo). 2012;67(9):1019-22. [ Links ]

Demirkol S, Balta S, Unlu M, Arslan Z, Cakar M, Kucuk U, et al. Neutrophils/lymphocytes ratio in patients with cardiac syndrome x and ıts association with carotid ıntima-media thickness. Clin Appl Thromb Hemost. 2014;20(3):250-5. [ Links ]

Received: May 7, 2014; Accepted: September 7, 2014

Correspondence to: Sevket Balta. Department of Cardiology. Eskisehir Military Hospital, Vişnelik Mah., Atatürk Cd. 26020 – Akarbaşı/Eskişehir, Turkey.

Disclosure: no potential conflict of interest relevant to this article was reported.

Creative Commons License This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.