The effect of over- and undertreatment of hypothyroidism on hospitalization outcomes of patients with acute decompensated heart failure (HF) has not been evaluated yet. We conducted retrospective cohort analyses of outcomes among 231 consecutive patients with treated hypothyroidism who were admitted to internal medicine departments of Shamir Medical Center with HF (2011-2019). Patients were divided into three groups according to their thyroid-stimulating hormone (TSH) levels: well treated (TSH: 0.4-4 mIU/L), overtreated (TSH: <0.4 mIU/L), and undertreated (TSH: >4 mIU/L). The main outcomes were mortality and recurrent hospitalization within 3 months. Among 231 patients, 106 were euthyroid, 14 were overtreated, and 111 undertreated. Patients' mean age was 79.8 ± 9.4 years. In-hospital mortality occurred in 4.7% in euthyroid patients, 14.3% in the overtreated group, and 10.7% in the undertreated group (p = 0.183). Differences in 30-day (p = 0.287) and 90-day (p = 0.2) mortality or recurrent hospitalization (p = 0.438) were not significantly different as well. However, in patients who were markedly undertreated and overtreated (TSH: >10 mIU/L or below 0.4 mIU/L) compared with 0.4-10 mIU/L, a significant increase in 90-day mortality was observed (33.3% vs 15.1% p = 0.016). Treatment status was independently associated with 90-day mortality after controlling for confounders with an adjusted odds ratio of 3.55 (95% confidence interval: 1.39-9.06). Although mild under- or overtreatment of hypothyroidism does not have a significant detrimental effect on hospitalization outcomes of patients with acute decompensated HF, markedly under- and overtreatment are independently associated with rehospitalizations and 90-day mortality. Larger cohorts are needed to establish the relationship between treatment targets and hospitalization outcomes of patients at risk for HF hospitalization.
Keywords: Hypothyroidism; heart failure; overtreatment; undertreatment.