THU265 A U-Shaped Relationship Between Undiagnosed Diabetes And Thyroid Function
Authors: Zafar Alvi Zara , Karnchanasorn Rudruidee , Ou Horng-Yih , Chuang Lee-Ming , George Gianoukakis Andrew , Chiu Ken C 
Published: October 2023

Abstract
Disclosure: Z.Z. Alvi: None. R. Karnchanasorn: None. H. Ou: None. L. Chuang: None. A.G. Gianoukakis: None. K.C. Chiu: None.
Thyroid dysfunction is present in about 20 million people in the United States, with about 60% percent unaware of their condition. Thyroid hormone is one of the key hormone regulators of energy metabolism, while diabetes mellitus (DM) is a disorder of dysregulated fuel metabolism. Thus, thyroid hormone can affect glucose metabolism. Unfortunately, this area has received little attention over the past few decades. This study investigates the rate of undiagnosed DM in relation to thyroid function. A representative and noninstitutionalized US adult (aged 20 years or older with BMI available) population from the National Health and Nutrition Examination Survey 2007-2012 was used for this study. Subjects with known thyroid diseases and/or diabetes were excluded. This study only included subjects with available TSH, free T4 (FT4), and free T3 (FT3) levels and the defined status of glucose tolerance by HbA1c, fasting, and/or 2-hour post-challenge plasma glucose concentrations (n=6,843). The rates of previously undiagnosed DM were determined for each quintile of TSH, FT4, and FT3 with sample-weighted analysis. The adjusted odds ratio (AOD) with a 95% confidence interval (95%CI) for DM was calculated with the lowest quintile as a reference after consideration of age, gender, BMI, and racial/ethnic groups. Amongst 6,834 subjects in this study, DM was found in 488 subjects. The rates of DM from quintile 1 to quintile 5 were 3.37%, 3.95%, 3.84%, 6.42%, and 7.26 % for TSH quintiles (P&lt;0.0001 by ANOVA); 5.69%, 4.27%, 5.05%, 4.74%, and 6.46% for FT4 quintiles (P&lt;0.0001 by ANOVA); and 4.82%, 4.63%, 5.33%, 5.33%, and 4.93% for FT3 quintiles (P&lt;0.0001 by ANOVA). Although the correlations were imperfect among TSH, FT4, and FT3 quintiles, the U-shaped relationship of DM with thyroid function was confirmed by the lowest AOD of 0.80 (95%CI: 0.80 - 0.80, P&lt;0.0001) for the 3rd quintile of TSH (TSH: 1.321 - 1.771 mIU/L). The association of DM with low thyroid function was confirmed by the AOD of 1.31 (95%CI: 1.30 - 1.32, P&lt;0.0001) for the 5th quintile of TSH (TSH: 2.519 - 80.968 mIU/L). The association of DM with high thyroid function was confirmed by AOD of 2.45 (95%CI: 2.44 - 2.46, P&lt;0.0001) for the 5th quintile of FT3 (FT3: 3.51 - 28.82 pg/mL). FT4 confirmed the U-shaped relationship with the highest AOD of 1.07 (95%CI: 1.07 - 1.08, P&lt;0.0001) for the 5th quintile of FT4 (FT4: 0.91 - 4.80 ng/mL) and the lowest AOD of 0.82 (95%CI: 0.82 - 0.82, P&lt;0.001) for the 2nd quintile of FT4 (FT4: 0.91 - 4.80 ng/mL). Our study revealed a U-shaped relationship between the rates of undiagnosed DM with thyroid function in a representative and noninstitutionalized US adult population without a prior diagnosis of thyroid dysfunction and diabetes. Different underlying mechanisms may be responsible for the association of DM with high and low thyroid function. Further studies are required to elucidate the underlying mechanisms.
Presentation: Thursday, June 15, 2023