Letter: Subclinical Hypothyroidism Is Independently Associated with Microalbuminuria in a Cohort of Prediabetic Egyptian Adults (Diabetes Metab J 2013;37:450-7)

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Diabetes Metab J. 2014;38(1):83-84

Publication date (electronic) : 2014 February 19

doi : https://doi.org/10.4093/dmj.2014.38.1.83

Department of Endocrinology and Metabolism, Kyung Hee University School of Medicine, Seoul, Korea.

Corresponding author: In-Kyung Jeong. Department of Endocrinology and Metabolism, Kyung Hee University School of Medicine, 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 130-701, Korea. jik1016@dreamwiz.com

Dear Editor,

It was with great interest that I read the article entitled "Subclinical hypothyroidism is independently associated with microalbuminuria in a cohort of prediabetic Egyptian adults" by El-Eshmawy et al. [1] in this journal.

The associations between diabetes, subclinical hypothyroidism (SCH), and vascular complications have important clinical implications because hypothyroidism itself is a risk factor of atherosclerosis through endothelial dysfunction, and microalbuminuria is an independent marker of cardiovascular diseases in patients with type 2 diabetes. They were the first to present a report about the association of SCH and albuminuria in prediabetic subjects. However, this study has some points that should be discussed.

Firstly, prediabetic subjects with SCH had higher levels of insulin resistance and microalbuminuria, but there was no significant association between the level of thyroid stimulating hormone (TSH) and hemoglobin A1c (HbA1c). Recently, Bilic-Komarica et al. [2] reported that TSH is correlated with HbA1c in patients with SCH. Also, they showed that the HbA1c level was reduced after 6 months of thyroid hormone replacement treatment in patients with SCH. Moreover, because insulinresistance and fasting insulin is associated with TSH, analysis for the reason why there was no correlation between TSH and HbA1c levels is needed.

Secondly, hypothyroidism patients usually have anemia. Anemia is a condition which leads to falsely elevated HbA1c levels. Christy et al. [3] recently reported that non-diabetic hypothyroidism subjects with anemia had elevated HbA1c levels in a prediabetic range. Since SCH can result in anemia, it would be advisable to examine the prevalence of anemia in this study population and the association between anemia and the level of HbA1c.

Thirdly, another study reported that the prevalence of SCH was 7.2% in type 1 diabetic patients [4]. Because the main cause of SCH is autoimmune thyroiditis, the prevalence of SCH can increase in patients with type 1 diabetes. However the mechanism for the increased incidence of SCH in prediabetic or type 2 diabetic subjects is not clear, therefore measurements of thyroid auto-antibody is necessary.

Fourthly, there are not many studies regarding the association between SCH and diabetic microvascular complications. A few previous studies from Taiwan [5], China [6], Korea [7], and Japan [8] demonstrated the association between them, but, there are some contradictory results. Chen et al. [5], Yasuda et al. [8], and this article [1] reported the association between SCH and diabetic nephropathy, but not with retinopathy. On the other hand, Yang et al. [6] and Kim et al. [7] demonstrated the association between SCH and diabetic retinopathy, but not with nephropathy. Therefore, further prospective studies are needed to confirm the exact association between SCH and diabetic microvascular complications in multiple ethnic groups and large prospective studies.

Notes

No potential conflict of interest relevant to this article was reported.

References

1. El-Eshmawy MM, Abd El-Hafez HA, El Shabrawy WO, Abdel Aal IA. Subclinical hypothyroidism is independently associated with microalbuminuria in a cohort of prediabetic egyptian adults. Diabetes Metab J 2013;37:450–457. 24404516.

2. Bilic-Komarica E, Beciragic A, Junuzovic D. Effects of treatment with L-thyroxin on glucose regulation in patients with subclinical hypothyroidism. Med Arh 2012;66:364–368. 23409511.

3. Christy AL, Manjrekar P, Babu RP, M S R, Hegde A. Elevation of HbA1C in non-diabetic hypothyroid individuals: is anaemia the connecting link? A preliminary study. J Clin Diagn Res 2013;7:2442–2444. 24392367.

4. Denzer C, Karges B, Nake A, Rosenbauer J, Schober E, Schwab KO, Holl RW. DPV Initiative and the BMBF-Competence Network Diabetes Mellitus. Subclinical hypothyroidism and dyslipidemia in children and adolescents with type 1 diabetes mellitus. Eur J Endocrinol 2013;168:601–608. 23384709.

5. Chen HS, Wu TE, Jap TS, Lu RA, Wang ML, Chen RL, Lin HD. Subclinical hypothyroidism is a risk factor for nephropathy and cardiovascular diseases in type 2 diabetic patients. Diabet Med 2007;24:1336–1344. 17941864.

6. Yang JK, Liu W, Shi J, Li YB. An association between subclinical hypothyroidism and sight-threatening diabetic retinopathy in type 2 diabetic patients. Diabetes Care 2010;33:1018–1020. 20150298.

7. Kim BY, Kim CH, Jung CH, Mok JO, Suh KI, Kang SK. Association between subclinical hypothyroidism and severe diabetic retinopathy in Korean patients with type 2 diabetes. Endocr J 2011;58:1065–1070. 21931224.

8. Yasuda T, Kaneto H, Kuroda A, Yamamoto T, Takahara M, Naka T, Miyashita K, Fujisawa K, Sakamoto F, Katakami N, Matsuoka TA, Shimomura I. Subclinical hypothyroidism is independently associated with albuminuria in people with type 2 diabetes. Diabetes Res Clin Pract 2011;94:e75–e77. 21925759.

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