The Thyroid-Heart Axis- Hormone Dynamics and Outcomes in Cardiogenic Shock Following Myocardial Infarction Short Title: Thyroid-Heart Axis in Cardiogenic Shock

Abstract Background Thyroid hormone alterations are common in critical illness and may reflect disease severity. However, their prognostic relevance in infarct-related cardiogenic shock remains insufficiently defined. Methods In this prospective cohort study from our Cardiogenic Shock Registry, 41 patients with acute myocardial infarction complicated by cardiogenic shock underwent serial measurements of thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), and free thyroxine (fT4) at baseline and 24, 48, and 72 hours after percutaneous coronary intervention. Associations between hormone trajectories and in-hospital mortality were assessed. Results Survivors exhibited significantly higher TSH levels over time compared to non-survivors. In contrast, non-survivors showed an early and sustained decline in fT3 and fT4. This hormonal pattern, consistent with low T3 and low T4 syndrome, was associated with adverse clinical outcomes. Conclusions Dynamic thyroid hormone changes—particularly persistent reductions in fT3, fT4, and TSH—were associated with in-hospital mortality in infarct-related cardiogenic shock. These findings suggest a potential prognostic role for thyroid function monitoring in acute cardiovascular critical illness.