Alterations in thyroid function tests in aged hospitalized patients: prevalence, aetiology and clinical outcome

Abstract

Thyroid dysfunction is common in aged people and has recently been associated to mortality. Our aims have been (1) to assess the prevalence of alterations in thyroid function tests in hospitalized patients over age 60 years and (2) to study the relationship between thyroid functional status and mortality during hospitalization. We studied a group of 447 patients (62% women), aged 61-101 year, hospitalized during 2005. Thyroid dysfunction was assessed by measuring serum concentrations of thyrotrophin (TSH), free thyroxine (FT4), and free thriiodothyronine (FT3). Thyroid autoimmune status was evaluated through thyroid peroxidase (TPO) and thyroglobulin (TG) antibodies quantification. Twenty-one patients (4.7%, 19 women) showed previously known thyroid dysfunction. 332 patients (74.3%) showed alterations in thyroid function tests. Euthyroid sick syndrome (ESS) was the derangement more frequently found (n = 278, 62.2%). After excluding ESS patients, 60 patients (13.4%) showed thyroid dysfunction: overt hypothyroidism, 14 (3.1%); subclinical hypothyroidism, 25 (5.6%); overt hyperthyroidism, 11 (2.5%), and subclinical hyperthyroidism, 10 patients (2.2%). Thyroid autoimmunity was positive in only 4.0% and 2.3% of patients, for TPOAb and TgAb, respectively. The presence of alterations in thyroid function tests was positively associated with the age of the patients and mortality during hospital stay (P < 0.001). Serum levels of FT3 were negatively related to death during hospitalization (OR 0.56; CI 95%, 0.38-0.81; P < 0.01). About three quarters of patients admitted in our geriatric unit exhibited alterations in thyroid function tests. This finding was associated with elevated age and poor prognosis. The reduction of FT3 values was a powerful predictor for mortality during hospitalization in elderly patients.