The levels of HbA1c in patients with thyroid dysfunction

Abstract

Thyroid hormones increase the hepatic glyconeogenesis, glycogenolysis and the absorption of glucose. Glucose intolerance is common in thyroid dysfunction. HbA1c is the most important determinant of long term glysemic status in diabetic patients. HbA1c is affected from various factors. In this study we evaluated the relation between thyroid function tests and HbA1c in non-diabetic patients with thyroid dysfunction. Non-diabetic 43 patients with hyperthyroidism, 20 patients with hypothyroidism and for control group 29 euthyroid patients which appealed to Ankara Numune Training and Research Hospital Internal Outpatient Clinic between June 2008 and January 2009 were recruited to this study. Fasting blood sugar, urea, creatinine, hemoglobine, HbA1c, TSH, FT3, FT4 and albumine levels of all of the patients that recruited to study were determined. There was no statistically significant difference for the mean age (p=0.271) and gender distribution (p=0.23) in the cases of hyperthyroidism, hypothyroidism and euthyroid controls. HbA1c levels were significantly higher in hyperthyroid group when compared to hypothyroid and euthyroid groups (p<0,001). Fasting blood glucose levels were found significantly higher in hyper thyroid group than hypothyroid and euthyroid groups (p=0.018). A positive correlation was revealed between the increasing age and HbA1c levels. A statistically significant difference was found in the levels of HbA1c values in patients with hyperthyroidism according to euthyroid and hypothyroid patients and this finding is in compliance with the results of current literature. This makes us to think that here is a relation between insulin resistance and hyperthyroidism. Therefore, it is suggested that monitorisation of blood glucose levels regularly is useful for the early diagnose of type II diabetes mellitus in patients with hyperthyroidism, both during the therapy and post treatment period. Keywords: Thyroid dysfunction, HbA1c, Insulin resistance Özet Tiroid hormonları hepatikglukoneogenezi, glikojenolizi ve intestinal glukoz emilimini arttırırlar. Tiroid disfonksiyonunda glukoz intoleransı sıkça karşılaşılan bir durumdur. HbA1c diyabetik hastalarda uzun süreli glisemik durumun değerlendirilmesinde en önemli belirteçdir. HbA1c düzeyi ise çeşitli faktörlerden etkilenebilmektedir. Biz bu çalışmamızda diyabetik olmayan yeni tanı konmuş tedavi almamış tiroid disfonskiyonu olan hastalarda tiroid fonksiyon testleri ve HbA1c arasındaki ilişkiyi inceledik. Bu çalışma Ankara Numune Eğitim ve Araştırma Hastanesi Dahiliye polikliniklerine ( Haziran -2009 Ocak) başvuran diyabetik olmayan ve ilk kez tanı alan 43 hipertiroidi ve 20 hipotiroidi hastasıyla 29 ötiroidili kontrol grubu arasında yapıldı. Çalışmaya katılan tüm olguların açlık kan şekeri, üre, kreatinin, hemoglobin, HbA1c, TSH, FT3, FT4, albümin değerlerine bakıldı. Hipertiroidi, hipotiroidi ve ötiroidi olguların yaş ortalamaları (p=0,271) ve cinsiyet dağılımları (p=0,23) açısından istatiski olarak anlamlı fark bulunmadı. Hipertiroidi grubunda HbA1c sev...

Thyroid hormones, blood glucose and glycosylated hemoglobin in healthy Sudanese subjects

“…24 In the present study a positive linear significant correlation was observed between the serum levels of T3, T4 and HbA1c. These findings are supported with other studies, showing that the level of HbA1c is elevated in hyperthyroidism p. 10,17 This result might be explained by the fact that, thyroid hormones facilitate the glycogenolytic and gluconeogenic effects of epinephrine and glucagon and stimulate hepatic gluconeogenic enzymes (phosphorenol pyruvate carboxykinase) increasing blood glucose level and so does HbA1c. Another explanation of the hyperglycemic effect of thyroid hormones could be their anti-insulin actions in different organs.…”

“…12,13 The higher levels of FBS and HbAlc in hyperthyroid group compared to normal controls appeared as changes of carbohydrate metabolism. [14][15][16][17] A significant correlation between TSH and HbA1c serum levels has also been found. 18 Low RBC turnover, with a predominance of older cells are associated with a falsely elevated HbA1c.…”

Clinical Associations of Thyroid Hormone Levels with the Risk of Atherosclerosis in Euthyroid Type 2 Diabetic Patients in Central China

“…Both overt and subclinical hypo- and hyperthyroid dysfunction were found associated with HbA1c level and T2D disease. HbA1c levels were significantly higher in the hyperthyroid group when compared with hypothyroid and euthyroid groups [ 19 ]. In this euthyroid T2D population, we found that HbA1c was negatively correlated with FT3 and positively correlated with FT4 and TSH.…”

Effect of Correction of Hyperthyroidism with Anti-thyroid Drugs on the Glycated Hemoglobin in Non-diabetic Patients with Primary Hyperthyroidism

“…However, studies on HbA1c in thyrotoxicosis are not consistent. Two studies reported that HbA1c was higher in hyperthyroid patients compared to euthyroid controls; however, one study had a higher fasting plasma glucose ( 12 ) in hyperthyroid patients, the other showed a trend toward higher mean plasma glucose ( 11 ) in hyperthyroid group. Thus, the higher HbA1c in hyperthyroid patients could be easily attributed to the higher glycemia in the hyperthyroid group of patients.…”

“…Hyperthyroidism has the opposite effect of increasing RBC turnover (increase in erythropoiesis accompanied by a shortened RBC survival time) ( 10 ), thereby causing a potential reduction in HbA1c relative to the level of glycemia. There are, however, conflicting reports of high ( 11 , 12 ) and low HbA1c ( 13 ) in hyperthyroidism compared to matched controls. But these studies were cross-sectional in nature.…”