Pre-admission TSH levels predict long-term mortality in adults treated for hypothyroidism

Context: Limited data is available regarding the association between pre-admission thyroid function and prognosis of hospitalized patients treated for hypothyroidism. Objective: Evaluate an association between thyroid stimulating hormone (TSH) levels and mortality in hospitalized levothyroxine-treated patients. Design and setting: Observational data of patients admitted to medical wards between 2011 and 2013. TSH levels obtained up to 180 days prior to admission were stratified as follows: low (≤0.5 mIU/L), normal (0.5–5 mIU/L), high (>5 mIU/L). Patients: Patients aged 60–80 years with available thyroid function tests were matched with controls without hypothyroidism. Main outcome: All-cause mortality up to 66-months following discharge. Results: One thousand and fifty seven patients (73% females, mean (SD) age 71 ± 6 years) were matched with controls without hypothyroidism. Mean hospital stay and in-hospital mortality were not different between groups. Mortality risk at the end-of-follow-up was 41% (438/1057) and 37% (392/1057) for patients with and without hypothyroidism (p < 0.05). TSH levels were classified as follows: low, 84 patients (8%); normal, 667 patients (63%); high, 306 patients (29%). Length of hospitalization and in-hospital mortality were not different between TSH categories. Mortality risk at the end-of-follow-up was 30, 39, and 50% with low, normal and elevated TSH, respectively. Adjusted hazard ratio (95% CI) of mortality at the end-of-follow-up was of 2.2 (1.2–3.8) for high vs. low TSH levels, and 1.4 (1.1–1.9) for high vs. normal TSH levels. Conclusion: In treated hypothyroid adult patients, increased TSH up to 6 months prior to admission is associated with increased mortality. Treatment should aim at achieving euthyroidism to improve survival.