Serum thyrotropin concentration is an early marker of normalization of low triiodothyronine syndrome in aged hospitalized patients after discharge

Abstract

Objectives: To assess short-term spontaneous evolution of alterations in thyroid function tests in aged hospitalized patients after discharge. Methods: A group of 146 patients (mean age±SD 85.9±6.2 yr) was studied. Serum concentrations of TSH, free T₄ (FT₄), and free T₃ (FT₃) were evaluated in every patient both after admission and 1 month after discharge. Results: At entry, both serum TSH [median (interquartile range), 2.19 mU/l (0.89–2.31)] and FT₄ (mean±SD, 16.7±3.4 pmol/l) concentrations were into the normal range, whereas serum FT₃ concentrations were low (3.3±0.7 pmol/l). After discharge TSH and FT₄ concentrations remained normal and FT₃ low. However, both serum TSH [2.53 mU/l (1.24–3.33); p<0.01] and FT₃ (3.7±1.0 pmol/l; p*#x003C;0.001) concentrations significantly increased. Most patients (no.=124, 84.9%) showed the euthyroid sick syndrome (ESS). After discharge, ESS diminished to 76 (52.1%) subjects. Patients who normalized thyroid function tests showed significantly lower TSH values at entry compared with those who persisted with altered thyroid function tests [1.27 mU/l (0.69–1.89) vs 1.69 mU/l (0.96–2.91), p<0.05]. Logistic regression analysis showed that serum levels of TSH at admission was the only variable negatively related to normalization of thyroid function [odds ratio 0.730; confidence interval 95%, 0.567–0.940; p=0.01). Conclusions: About 35% of aged patients hospitalized for acute illness spontaneously normalize their thyroid function tests 1 month after discharge, mainly due to the correction of ESS. Serum TSH levels at admission seem to be the only variable negatively related to normalization of thyroid function at this time.