Association of subclinical hypothyroidism and HbA1c levels in non-diabetic subjects attending rural tertiary care centre in central India

Abstract

NTRODUCTIONThyroid disorders are very common in the general population and is second most common condition affecting the endocrine system after diabetes mellitus. Decreased production of thyroid hormone is the key feature of hypothyroidism.2 Subclinical hypothyroidism is defined as an elevated serum TSH level and normal concentrations of free T3 (FT3), free T4 (FT4), T3 and T4.1 It is often complicated by conditions such as dilutional hyponatremia, anaemia and hyperlipidemia. Subclinical hypothyroidism is more common in the elderly and is more prevalent in women than in men. 4,5 The American Diabetes Association (ADA) have approved the use of HbA1c for the screening and the diagnosis of diabetes. 6 The HbA1c concentration not only depends on prevailing glycaemia but also the life span of the erythrocytes and so, the conditions which affect the erythrocyte turnover or survival may lead to falsely elevate or lower the HbA1C levels.7-11 A positive association between thyroid and diabetes mellitus is well recognized but to study the effect of thyroid disorders on glucose metabolism in non-diabetic patients is an area for extensive research. Recent studies have shown its spurious elevation in hypothyroidism in the absence of diabetes.1,2 Present study was planned to assess ABSTRACTBackground: Subclinical hypothyroidism is defined as an elevated serum TSH level and normal concentrations of free T3 (FT3), free T4 (FT4), T3 and T4. A positive association between thyroid and diabetes mellitus is well recognized but to study the effect of thyroid disorders on glucose metabolism in non-diabetic patients is an area for extensive research. Present study was planned to assess correlation between subclinical hypothyroidism and glycosylated haemoglobin levels in non-diabetic patients. Methods: A case-control study was conducted on total 209 subjects. 109 patients were allotted in case group and 100 in control group. Controls were relatives and friends of patients who were matched for age and sex. Comparison between the case and the control groups were made using Student's t-test (unpaired) and Box and Whisker Plot and regression graph were presented for correlation between serum TSH and HbA1c. Results: It was found that there was a positive correlation between the levels of serum TSH (µU/L) and HbA1c (%) in all the participants of the study by Pearson's correlation coefficient (r=0.35, p < 0.0001). Conclusions: HbA1c levels are increased in subclinical hypothyroid patients. The effects of the elevated levels of Serum TSH on the HbA1c must be considered when interpreting the HbA1c for the diagnosis of diabetes or prediabetes in the subclinical hypothyroid patients.

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“…The Male : Female sex ratio was 2.33 and 3.44 was comparable to each other (X 2 =0.24, df=1,p>0.05) The parameters were significantly higher like; FPG (mg/dl)-91.56±7.89 and 80.92±5.82 (t=7.28,df=88,p<0.0001); HbA1C-7.12± 3.45 and 5.34± 2.91 (t=9.83,df=88,p<0.0001); Fructosamine (μmol/L)-593.87±56.89 and 257.92±8.95 (t=5.73,df=88,p<0.001) in Hypothyroid group as compared to Euthyroid group respectively. These findings are similar to Ram VS et al 26 et al they found that there was a positive correlation between the levels of serum TSH (µU/L) and HbA1c (%) in all the participants of the study by Pearson's correlation coefficient (r=0.35, p < 0.0001). Also Sridevi V. Udup 27 they found that The fructosamine levels were significantly higher in Hypothyroid as compared to euthyroid group (p<0.05),…”

HbA1c-deceptive Levels in Subclinical Hypothyroidism?

“…This is in accordance with other studies which had also reported similar results. 9,[12][13][14][15][16] We had excluded those with anaemia and no significant difference was found in haemoglobin levels in both groups. Some studies have found reduced erythropoiesis/ anaemia to be related to elevated HbA1c levels.…”

“…7 There are some studies that have brought out the relationship between elevated HbA1c levels and subclinical hypothyroidism in non-diabetic individuals. [8][9][10] Increase in HbA1c levels in non-diabetic subjects was also related to the coexistence of anaemia in hypothyroid patients. 11 In our study, we have attempted to assess the HbA1c levels among non-diabetic participants and determine its association with subclinical hypothyroidism, in a small south Indian population.…”

Glycated Haemoglobin (HbA1c) Variations in Nondiabetics With Nutritional Anemia

“…The American Diabetes Association (ADA) included HbA1c alone as a diagnostic tool for diabetes in 2010 [1], and we still consider HbA1c a reliable marker for diabetes control as per the 2018 ADA guidelines [8]. Factors altering HbA1c concentrations are Hb variants [9], hemolytic anemia, renal failure [10], hypothyroid [11], alcoholism, and hyperbilirubinemia. In this study, we aimed to look for HbA1c variations in nutritional anemia and their consideration with HbA1c as a diagnostic tool.…”