Dear Editor,

I read with interest the study by Al Fahdi et al,1 published in the May 2022 issue of the Oman Medical Journal. The authors studied thyroid dysfunction (TD) among Omani patients with chronic kidney disease (CKD) and found that 11.7% of CKD patients had TD. Of these, 62.9% had subclinical hypothyroidism and 37.1% had subclinical hyperthyroidism. They concluded that TD coexisted with kidney dysfunction and these hormonal axis dysfunctions might not be evident at initial presentation and, therefore, might necessitate regular clinical and laboratory evaluations.1 Apart from a few study limitations presented by the authors, we believe that the following limitation is noteworthy. The precise assessment of thyroid gland functions for a particular population needs a referral to the thyroid hormones normative data (THND). Since the determinants of age, gender, weight, genetic background, and ethnicity control THND,2 certain populations-specific THND have been built.3–5 The normal range for thyroid-stimulating hormone of 0.2–4.5 mIU/L and 8–24 pmol/L for free thyroxin were considered in assessing thyroid health status in the studied CKD cohort. However, the reference of the employed THND was not addressed. This limitation might additionally debate the rightness of the study results. We believe that relying upon the national THND rather than a foreign standard could better discern the prevalence and pattern of TD among CKD patients. Hence, we suggest the construction of Omani THND and its employment in clinical fields and research settings.

references

1. 1. Al Fahdi I, Al Salmi I, Al Rahbi F, Shaheen F, Hannawi S. Thyroid dysfunction and kidney dysfunction. Oman Med J 2022 May;37(3):e377.
2. 2. Chaker L, Korevaar TI, Medici M, Uitterlinden AG, Hofman A, Dehghan A, et al. Thyroid function characteristics and determinants: the Rotterdam study. Thyroid 2016 Sep;26(9):1195-1204.
3. 3. Musa IR, Ali NI, Elseed SA, Osman OE, Adam I. Reference intervals of thyroid hormones in Khartoum, Sudan. BMC Res Notes 2018 Oct;11(1):729.
4. 4. Zou Y, Wang D, Cheng X, Ma C, Lin S, Hu Y, et al. Reference intervals for thyroid-associated hormones and the prevalence of thyroid diseases in the Chinese population. Ann Lab Med 2021 Jan;41(1):77-85.
5. 5. Oblak A, Biček A, Pirnat E, Zaletel K, Gaberšček S. First estimation of reference intervals for thyroid-stimulating hormone and thyroid hormones in Slovenian population. Acta Chim Slov 2021 Jun;68(2):488-493.