Bidirectional Association between Thyroid Function and Glycemic Status: A Cross-Sectional Study

Abstract

Aim: Diabetes and thyroid dysfunctions have similar mechanisms, and they may be overlooked or undiagnosed. This study aimed to evaluate the effect of thyroid hormone levels on glycosylated hemoglobin (HbA1c) and the thyroid-diabetes relationship. Material and Methods: HbA1c, glucose, free T3 (fT3), free T4 (fT4), and thyroid-stimulating hormone (TSH) values measured in the same samples of patients aged 18 and 60 years were obtained. Normoglycemic individuals were divided into subgroups as normal, hypothyroidism, and hyperthyroidism according to their TSH levels (Model 1), and non-thyroid dysfunction patients were divided into normoglycemic, prediabetic, and diabetic subgroups according to their HbA1c levels (Model 2). Correlations and differences of the obtained data were analyzed. Results: In Model 1, the median HbA1c level was 5.44 (range, 5.08-5.68) in the hyperthyroidism group, which was significantly higher than normal (5.32; range, 4.96-5.69) and hypothyroidism (5.33; range, 5.02-5.65) groups (p=0.021). In Model 2, fT3 levels were found significantly higher in normoglycemic patients (3.11; range 1.95-3.75 pg/ml) than prediabetic (3.01; range, 2.13-3.82 pg/ml), and diabetic (3.00; range, 2.02-3.69 pg/ml) patients (p=0.001), while fT4 levels in diabetic patients (1.29; range, 0.56-1.74 ng/dl) were significantly higher compared to normoglycemic (1.23; range 0.72-1.89 ng/dl), and prediabetic (1.24; range, 0.73-1.66 ng/dl) patients (p=0.003). Conclusion: The results showed that HbA1c levels could be a marker for thyroid function in non-diabetic individuals. In diabetic patients, thyroid hormone balance and ratios are changing. For better glycemic control and the prevention of complications, regular thyroid function screenings are recommended, especially in individuals with a predisposition to diabetes.

Keywords

• Glycemic control
• Hemoglobin A1c
• thyroid dysfunction

Tiroid Fonksiyonu ve Glisemik Durum Arasındaki Çift Yönlü İlişki: Kesitsel Bir Çalışma

Öz

Amaç: Diyabet ve tiroid fonksiyon bozuklukları benzer mekanizmalara sahiptir ve gözden kaçabilir veya tanı konulamayabilir. Bu çalışmanın amacı, tiroid hormon düzeylerinin glikolize hemoglobin (HbA1c) üzerindeki etkisinin ve tiroid-diyabet ilişkisinin değerlendirilmesidir. Gereç ve Yöntemler: Yaşları 18 ve 60 arasında olan hastaların aynı örneklerinde ölçülen HbA1c, glikoz, serbest T3 (fT3), serbest T4 (fT4) ve tiroid uyarıcı hormon (thyroid-stimulating hormone, TSH) değerleri elde edildi. Normoglisemik bireyler TSH düzeylerine göre normal, hipotiroidi ve hipertiroidi olarak alt gruplara ayrılırken (Model 1), tiroid fonksiyon bozukluğu olmayan hastalar HbA1c düzeylerine göre normoglisemik, prediyabetik ve diyabetik olarak alt gruplara ayrıldı (Model 2). Elde edilen verilerin korelasyonları ve farklılıkları analiz edildi. Bulgular: Model 1'de hipertiroidi grubunda ortanca HbA1c düzeyi 5,44 (aralığı 5,08-5,68) olup normal (5,32; aralığı 4,96-5,69) ve hipotiroidizm (5,33; aralığı 5,02-5,65) gruplarından anlamlı derecede daha yüksekti (p=0,021). Model 2'de, fT3 düzeyleri normoglisemik hastalarda (3,11; aralığı 1,95-3,75 pg/ml), prediyabetik (3,01; aralık 2,13-3,82 pg/ml) ve diyabetik (3,00; aralık 2,02-3,69 pg/ml) hastalara kıyasla anlamlı derecede daha yüksek bulunurken (p=0,001), fT4 düzeyleri ise diyabetik hastalarda (1,29; aralık 0,56-1,74 ng/dl) normoglisemik (1,23; aralık 0,72-1,89 ng/dl) ve prediyabetik (1,24; aralık 0,73-1,66 ng/dl) hastalara kıyasla anlamlı derecede daha yüksekti (p=0,003). Sonuç: Sonuçlar, HbA1c düzeylerinin diyabetik olmayan bireylerde tiroid fonksiyonları için bir belirteç olabileceğini göstermiştir. Diyabetik hastalarda tiroid hormon dengesi ve oranları değişmektedir. Daha iyi glisemik kontrol ve komplikasyonların önlenmesi için, özellikle diyabete yatkınlığı olan bireylerde düzenli tiroid fonksiyon taramaları önerilmektedir.

Anahtar Kelimeler

• Glisemik kontrol
• Hemoglobin A1c
• tiroid disfonksiyonu

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