Understanding the Drivers of Hypothyroidism in Patients Undergoing Chronic Hemodialysis

<b>Background/Objectives</b>: Hypothyroidism is highly prevalent among HD patients, due to cumulative disturbances in thyroid hormone synthesis, metabolism, and clearance. Subclinical hypothyroidism-defined by elevated TSH with normal fT₄-is common in HD, along with a distinct entity, the low-T₃ syndrome. This study aims to examine the predictors of hypothyroidism in HD and its impact on cardiovascular morbidity and mortality. <b>Methods</b>: We conducted a retrospective cohort study including 282 hemodialysis (HD) patients, with evaluated thyroid function and monitored from January 2022 to June 2025. A total of 66 (23.4%) patients with hypothyroidism were identified, 15 (5.31%) of whom had autoimmune thyroiditis. Subclinical hypothyroidism was documented in 31.81% of the hypothyroid patients. <b>Results:</b> Hypothyroidism occurred predominantly in females (63.63% vs. 41.2%, <i>p</i> ≤ 0.001) and was associated with higher BMI (27.856 ± 6.216 vs. 25.759 ± 6.080, <i>p</i> = 0.017), hypoalbuminemia (3.534 ± 0.547 vs. 3.725 ± 0.471, <i>p</i> = 0.006), elevated LDL-cholesterol and triglyceride levels, as well as with amiodarone use. Hypothyroidism was further associated with atrial fibrillation (33.33 vs. 19.9%, <i>p</i> = 0.022), coronary artery revascularization procedures (18.18% vs. 9.72%, <i>p</i> = 0.047), neoplastic disease (25.75% vs. 12.03%, <i>p</i> = 0.008), and cancer-related mortality (10.6% vs. 1.85%, <i>p</i> = 0.001). Multivariable regression analysis revealed the following predictors of hypothyroidism: female sex (OR 3.848, 95%CI 1.704-8.693, <i>p</i> = 0.001), BMI (OR 1.072, 95%CI 1.007-1.146, <i>p</i> = 0.031), hypoalbuminemia (OR 0.412, 95%CI 0.177-0.962, <i>p</i> = 0.040), hypertriglyceridemia (OR 1.088, 95% CI 1.001-1.016, <i>p</i> = 0.022) and amiodarone use (OR 6.698, 95%CI 1.744-25.722, <i>p</i> = 0.006). Patients with autoimmune thyroiditis did not exhibit clinical or biochemical differences compared with other hypothyroid patients. Subclinical hypothyroidism was associated with longer HD duration (10.476 ± 7.910 vs. 6.567 ± 5.541, <i>p</i> = 0.003), dyslipidemia, hypertension, atrial fibrillation and amiodarone use. Cardiovascular conditions-particularly atrial fibrillation and ischemic coronary disease requiring revascularization-are more common in HD patients with clinical or subclinical hypothyroidism. However, in our cohort, the Kaplan-Meier survival curves at 12, 24, and 36 months for patients with both subclinical and clinical hypothyroidism do not show significant differences in cardiac or overall mortality. <b>Conclusions</b>: The increased incidence of hypothyroidism in HD patients, together with its impact on cardiovascular pathology, underscores the need for multidisciplinary management and supports annual routine assessment of thyroid hormones-particularly in overweight or dyslipidemic patients and in those receiving amiodarone.