Thyroid Hormone Sensitivity Indices as Novel Predictors of Glycemic Instability and Hypoglycemia in Type 2 Diabetes

Purpose To investigate whether baseline thyroid hormone sensitivity indices can predict glycemic variability (GV) in patients with type 2 diabetes mellitus (T2DM) following inpatient glycemic stabilization. Methods We enrolled hospitalized T2DM patients with normal thyroid function who underwent at least six days of continuous glucose monitoring (CGM). Day 6 CGM data were selected for analysis to represent a period of glycemic stabilization. GV metrics included mean amplitude of glycemic excursions (MAGE), largest amplitude of glycemic excursions (LAGE), coefficient of variation (CV), and standard deviation (SD). We calculated baseline thyroid sensitivity indices, including the thyroid feedback quantile-based index (TFQI), thyrotroph TSH index (TSHi), thyrotroph T4 resistance index (TT4RI), and the FT3/FT4 ratio. Associations were analyzed using linear and logistic regression. Results Glycemic variability progressively decreased during the six-day observation period. Patients were stratified using a clinically relevant MAGE threshold (< 3.9 vs. ≥3.9 mmol/L).. Higher baseline TFQI and TSHi levels were significantly associated with greater Day 6 MAGE and CV. TFQI was positively associated with Day 6 MAGE (β = 1.382, P  < 0.001) and CV (β = 0.0454, P  < 0.001), while TSHi was associated with MAGE (β = 0.825, P  < 0.001). Logistic regression revealed that a higher TFQI independently predicted high GV (OR 3.11, 95% CI 1.27–7.60, P  = 0.013) and an increased risk of hypoglycemia (OR 4.78, 95% CI 1.56–14.63, P  = 0.006).. Conclusion Baseline thyroid hormone sensitivity is an independent predictor of glycemic instability after inpatient glucose optimization. These indices may serve as valuable clinical tools to guide decision-making and personalize treatment strategies for hospitalized patients with T2DM.