All-cause mortality, circulatory risk confirmed in hyperthyroidism

International Thyroid Congress

PARIS — A new study confirmed that patients with hyperthyroidism are at an increased risk for excess all-cause mortality, mainly related to circulatory causes.

“Furthermore, these data indicate that administration of doses of radioactive iodine sufficient to induce hypothyroidism is associated with significantly improved survival compared with doses of I-131, which render subjects euthyroid or with treatment with antithyroid drugs only,” Kristien Boelaert, MD, of the School of Clinical and Experimental Medicine at University of Birmingham, U.K., and colleagues said in a presentation here at the International Thyroid Congress.

Their study examined mortality in 1,127 patients who presented with a first episode of overt hyperthyroidism. The researchers considered the influence of treatment, disease etiology and pre-existing comorbidities on mortality outcomes. At the start of the study, 25% of the patients had pre-existing comorbidities, including arrhythmias, cancer and ischemic or valvular heart disease.

During a mean follow-up of 10 years, or 11,636 person-years, 315 patients with hyperthyroidism died compared with 256 expected deaths calculated using age- and period-specific mortality in England and Wales. The all-cause standard mortality rate (SMR) was 1.23 (95% CI, 1.10-1.38). Further, mortality related to circulatory causes (SMR=1.30; 95% CI, 1.09-1.55) and respiratory causes (SMR=1.38; 95% CI, 1.05-1.81) were significantly increased. Boelaert and colleagues noted no effect of the underlying etiology of hyperthyroidism, such as Graves’ disease or toxic nodular disease, on mortality.

The researchers examined the effect of treatment on mortality using data from 712 patients who were assigned to radioiodine ablation with I-131 and 415 who were assigned to antithyroid drugs. One year after I-131, 457 patients had become hypothyroid and 255 euthyroid.

All-cause mortality was significantly increased in patients treated with thionamides alone (SMR=1.39; 95% CI, 1.16-1.67), as well as in those rendered euthyroid after I-131 (SMR=1.30; 95% CI, 1.08-1.56). However, the same risk was not present for patients taking levothyroxine replacement after radioiodine (SMR=1.02; 95% CI, 0.83-1.26).

Examined further, the researchers found increased deaths from circulatory (SMR=1.62; 95% CI, 1.23-2.14) and respiratory causes (SMR=1.83; 95% CI, 1.19-2.81) in patients treated with thionamides only, but not those who received I-131.

Multivariate analysis that adjusted for age, sex, underlying etiology, treatment modality, smoking status and other factors confirmed a reduced HR for overall mortality in patients rendered hypothyroid after I-131 therapy (HR=0.69; 95% CI, 0.52-0.91) but not in those rendered euthyroid after radioiodine (HR=0.95; 95% CI, 0.72-1.24), when compared with patients who received thionamides only. – by Katie Kalvaitis

These are very important data showing that control of the hyperthryoid state is important in adults with refractory hyperthyroidism. The long term benefit of treatment with I-131 as compared to medical therapy is demonstrated with a clear reduction in mortality in the I-131 treated individuals.

–Scott A. Rivkees, MD

Chief of the Yale Pediatric Thyroid Center and Yale Child Health Research Center

For more information:

Boelaert K. OC-094. Presented at: the 14th International Thyroid Congress; Sept. 11-16, 2010; Paris.

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