Increased reverse triiodothyronine is associated with shorter survival in independently-living elderly: the Alsanut study

Abstract

ObjectiveIncreased reverse tritiodothyronine (T3) used to be described as a part of euthyroid sick syndrome (ESS). It was demonstrated to be associated with increased mortality in acutely ill patients. It can also be found with low or normal T3 in non-severely ill subjects but its significance remains unclear.Patients and designThe Alsanut study included a representative sample of 440 independently-living subjects aged 65 or over constituted between January 1988 and September 1989. Past and current medical history and nutritional data were collected at inclusion. Baseline thyroid hormone (TSH, FT4, FT3 and rT3) serum levels were measured. Life status was determined on 1 December 2005.ResultsOf the 374 elderly subjects included in the final analysis, 52 had abnormal TSH (43 with hyperthyroidism, nine with hypothyroidism) and 80.7% had died by 1 December 2005. There was no statistical difference in survival between subjects according to thyroid function (P=0.54). Of the 322 elderly subjects with normal TSH, mortality rate was 81.1%. ESS was found in 3.4%, whereas 8.1% of the participants displayed elevated rT3 with normal FT3. Time to death was strongly related to rT3 (P<0.0001) and FT3 (P<0.0001) in a univariate analysis. After adjusting for other confounding variables, rT3 was the only thyroid hormone associated with shorter survival (P=0.014).ConclusionsRT3 was the only thyroid hormone associated with shorter survival in a representative population of independently-living elderly. In these subjects, isolated elevated rT3 might be an equivalent of ESS, reflecting declining health.