The Association Between Elevated Thyroid-Stimulating Hormone Levels and Prolonged Length of Stay Among Adult Diabetic Patients Hospitalized in Internal Medicine Departments: A Large Historical Cohort Study.

: Type 2 diabetes mellitus (DM2) and hypothyroidism are two of the most common endocrine disorders in clinical practice. Hospital length of stay (LOS) is a quality metric of the health systems. We evaluated the association between elevated thyroid-stimulating hormone (TSH) levels and prolonged LOS among all adult patients (age ≥ 18 years) with DM admitted to our Internal Medicine departments between 2014 and 2022. : Data on patient characteristics, LOS, and in-hospital mortality were collected. A TSH level > 4.7 μIU/mL was considered as being elevated. A LOS > 75th percentile and in-hospital mortality were defined as being prolonged. Univariate and multivariable analyses were applied, and propensity score matching controlled for differences between patients with normal and those with elevated TSH levels. : Of the 19,066 study participants (median age 75.6 years, IQR 75.9-83.3), 1524 (7.9%) had elevated TSH levels, and prolonged LOS was significantly more common among them (before matching: 38.6% vs. 29.1%, < 0.001; after matching: 38.7% vs. 32.6%, = 0.001). After adjustment for potential confounders, elevated TSH levels were also associated with prolonged LOS (OR = 1.22, 95% CI 1.07-1.39, = 0.002). Elevated TSH levels in diabetic patients hospitalized in Internal Medicine departments are associated with prolonged LOS, emphasizing the importance of identifying hypothyroidism among them.