Published: Oct 31, 2013 | Updated: Nov 1, 2013
By Michael Smith, North American Correspondent, MedPage Today

Full Story:  http://www.medpagetoday.com/Endocrinology/Thyroid/42618

Among older patients hospitalized for an acute illness, thyroid hormone levels appeared to predict the risk of death — whether as inpatients or within 7 years after discharge, researchers reported.

In particular, low serum levels of free triiodothyronine (FT3) were associated both with death in hospital and with long-term mortality, according to Pedro Iglesias, MD, of  Hospital Ramón y Cajal in Madrid, and colleagues.

On the other hand, levels of thyroid stimulating hormone (TSH or thyrotropin) and free thyroxine (FT4) weren’t significantly associated with mortality after multivariate analysis,Iglesias and colleagues reported online in the Journal of Clinical Endocrinology & Metabolism.

“When older individuals have low levels of thyroid hormones, particularly T3, it reflects that the body is weak and more susceptible to the harmful effects of disease,” Iglesias said in a statement.

“As a result, older individuals who have a reduced ability to synthesize T3 hormones have a higher rate of mortality, both in the short- and long-term,” he added.

The findings come from a prospective observational cohort of 404 people, with an average age of 85.9, who were admitted to hospital for a range of acute conditions during 2005 and followed for seven years, Iglesias and colleagues reported.

On admission, they were given thyroid function tests, looking at levels of TSH, FT3, and FT4. The researchers hypothesized that one or more might predict mortality.

All told, 61 participants died while in the hospital and another 262 died later, the researchers reported.

Of the 81 survivors, the investigators found, most had normal levels of all three hormones, although the proportion of those with normal FT3 was only 54.3%, the percentage of those with normal TSH and FT4 were both above 88%

Of the 61 who died in hospital, most had normal TSH and FT4 but only nine patients had normal FT3, and the remaining 52 (85.2%) had low levels of the hormone.

The pattern was similar for those who died after discharge, the researchers found, but the disparity in FT3 levels was not as great — 170 (or 64.9%) had low levels and 91 (or 34.7%). One patient who died had a high FT3 level.

Of the 144 patients who had normal FT3 levels at the start of the study, only nine (6.2%) died while hospitalized, “making that finding highly predictive of survival,” the researchers reported.

In a multivariate analysis, the researchers found, significant predictors of all-cause mortality were a history of cancer, age, and FT3 levels, at P=0.003, P=0.009, and P<0.001, respectively.

For cardiovascular mortality, the same three emerged as significant factors (at P=0.003,P=0.027, and P=0.004, respectively) in the multivariate analysis, they reported.

One clinical implication is that “T3 could be a useful measure for gauging an older individual’s chances of surviving an acute illness requiring hospitalization,” Iglesias said.