HealthDay News — Synthetic levothyroxine (LT4) is associated with an increased risk for death among older adults, according to a study presented at the virtual meeting of The Endocrine Society, held from March 28 to 31.
Enoch Joseph Abbey, M.D., M.P.H., from the Johns Hopkins Medical Institute in Baltimore, and colleagues examined the effects of LT4 on survival in a cohort of 1,054 participants of the Baltimore Longitudinal Study of Aging aged 65 years or older. Thyroid status was defined at each visit, and differential survival was analyzed across thyroid function.
The researchers found that LT4 treatment was present in 13.7 percent of visits. For treated and untreated visits, there was no clinical difference in markers of health status. Patients were followed for a cumulative time of 8,483.3 years, during which there were 245 deaths. Regardless of thyroid-stimulating hormone (TSH), visits on LT4 contributed a higher risk for death compared with those who were euthyroid and not on thyroid hormone (hazard ratio, 1.55; 95 percent confidence interval, 1.00 to 2.38) and an estimated doubling of risk versus those with untreated isolated elevated TSH (hazard ratio, 2.23; 95 percent confidence interval, 1.05 to 4.73) after adjustment for confounding variables. On limiting analyses to those who were never overtreated, the results persisted (hazard ratio, 2.50; 95 percent confidence interval, 1.18 to 5.30).
“Our work supports the growing calls to use age-specific TSH reference intervals to determine the threshold for thyroid hormone treatment,” a coauthor said in a statement.