Higher levels of free thyroxine associated with increased risk of mortality

thyroid hormone

In a report presented at the Endocrine Society meeting, researchers have found that higher levels of free thyroxine in elderly euthyroid men are associated with an increased risk of all- cause mortality. It is already a known fact that thyroid disease and subclinical thyroid function are linked with increased mortality. But this is for the first time that the researchers tried to explore the relationship between thyroid hormones and mortality in men with normal thyroid functions.

For their study, the researchers led by Bu Beng Yeap from the University of Western Australia, Perth, followed up 3,885 men between the ages of 70 and 89 who were a part of the study Health in Men, for nine years. The research did not include men with known thyroid disease. During the follow up period, 21.5 percent of the participants expired. The researchers observed that the average age of the persons who had died was 78.5 years at the start of the study compared to other participants whose average age was 76.6 years at the start of the study. It was also seen that the levels of free thyroxine were significantly higher in the participants who died (16.2pmol/L) compared to other participants (15.8pmol/L).

The researchers adjusted for other confounding factors like age, smoking, blood pressure, body mass index, waist to hip ratio, blood levels of lipids and creatinine, and other associated diseases. Even after the adjustment, the researchers observed that the levels of free thyroxine were linked to an increased risk of mortality due to any cause.

The researchers have expressed the view that free thyroxine is not directly responsible for the mortalities. But it may be a marker of some other factor which may be behind the increased risk of mortalities. However, free thyroxine may be exerting some adverse effects on the cardiovascular health of the individuals. Earlier studies have demonstrated a link between free thyroxine and dementia. Further studies are required to identify the underlying mechanisms which cause an association between free thyroxine and increased risk of mortality.

Editor: Dr. Bimal Rajalingam MBBS DNB (Resp Med)


Friday, June 21, 2013