Association between reverse triiodothyronine and cardiac complications in patients with uncontrolled Graves' disease

Cardiac complications associated with poorly controlled Graves' disease present a significant challenge in managing hyperthyroid patients. The relationship between thyrotoxicosis severity and cardiac complications remains to be confirmed. This study investigates the association between reverse triiodothyronine (rT3) and cardiac complications in hospitalized patients with uncontrolled Graves' disease.

This cross-sectional study evaluated 178 hospitalized patients with uncontrolled Graves' disease from 2016 to 2020. After excluding cardiac diseases unrelated to Graves' disease, atrial fibrillation and heart failure were identified as direct outcomes of uncontrolled thyrotoxicosis. Data were extracted from the Hospital Inpatient Sample database, including demographic information, disease duration, comorbidities, and serum thyroid hormone levels. Restricted cubic splines and multivariate logistic regression models were used to assess the association between serum rT3 levels and cardiac complications related to thyrotoxicosis.

Among the 178 patients, 94 (54.0%) had cardiac complications. Multivariable logistic regression models adjusted for potential confounders (age, sex, duration of hyperthyroidism, diabetes, hypertension, and laboratory parameters) demonstrated a linear dose-response relationship between serum rT3 concentrations and cardiac complications. For each 1 nmol/L increase in rT3, the odds of cardiac complications rose by 65% (OR 1.65, 95% CI 1.28-2.14; P < 0.001). Subgroup analyses stratified by median age (50 years), median disease duration (12 months), sex, and anemia status showed that this association was consistent across all subgroups.

Elevated serum rT3 is a robust biomarker for atrial fibrillation and heart failure in uncontrolled Graves' disease and associates with greater hyperthyroidism severity and related cardiac complications.