Bauer DC et al. (2007) Thyroid hormone use, hyperthyroidism and mortality in older women. Am J Med 120: 343–349

Despite the widespread use of thyroid hormone in older women (aged ≥65 years), its effect on mortality has not been well studied. To investigate the relationship between thyroid hormone usage, thyroid dysfunction and mortality in older women, Bauer et al. performed a prospective cohort study in patients with and without thyroid disorders.

Of the 9,449 women evaluated, 12% were taking thyroid hormone at baseline, with a mean treatment duration of 15.8 years. A history of hyperthyroidism was reported in 9.4% of patients. Over 11.9 years' follow-up, 3,159 deaths were recorded, mainly from cardiovascular causes and cancer.

Overall, age-adjusted analyses showed that a history of hyperthyroidism was associated with increased mortality (relative hazard [RH] 1.20, 95% CI 1.06–1.36, after adjusting for thyroid hormone use, weight, health, exercise levels, diabetes, hypertension, and use of alcohol, tobacco, estrogen and thiazides). A history of hyperthyroidism was also associated with increased cardiovascular mortality on multivariate analysis (RH 1.46, 95% CI 1.20–1.77). This association was similar among the subset of women in whom TSH was measured.

Although age-adjusted analyses showed an association between thyroid hormone use and mortality, no association was seen on multivariate analysis. Likewise, no significant association was observed between thyroid hormone use and cardiovascular or cancer mortality, nor between the level of TSH and mortality in a subcohort of 487 patients.

While the results of this study are reassuring for elderly women taking thyroid hormone, further confirmatory studies are needed.