(HealthDay News) – For the oldest old, increases in thyroid-stimulating hormone (TSH) occur over time but do not correlate with mortality, according to a study published online Aug 9 in the Journal of Clinical Endocrinology & Metabolism.

Avantika C. Waring, MD, from the University of California in San Francisco, and colleagues described longitudinal changes in thyroid function in a cohort of 843 participants (mean age, 85 years) in the Cardiovascular Health Study All-Stars Study, who were not taking thyroid medication. The association between thyroid function (measured in 1992–1993 and 2005–2006) and mortality (through February 2011) was assessed.

Over the 13-year period, the researchers identified a significant increase in TSH (13%) and free T4 (FT4; 1.7%), and a significant decrease in total T3 (13%). During a median of 5.1 years of follow-up there were 287 deaths. Subclinical hypothyroidism, TSH level, and persistent thyroid peroxidase antibody positivity did not correlate with mortality, but there was a significant positive correlation between FT4 and mortality (hazard ratio per ng/dL, 2.57).

“Although we found neither a positive nor negative impact of TSH on mortality, higher FT4 levels were associated with death in this cohort,” the authors write. “Our findings suggest that reflexively treating mild elevations in TSH in those of advanced age is unnecessary.”

Full Text (subscription or payment may be required)