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Hyperthyroidism increased risk for all-cause mortality, circulatory disorders
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Patients aged at least 40 years with overt hyperthyroidism have an increased risk for mortality from all causes and circulatory diseases, recent study data suggest. Additional findings demonstrated that excess mortality was not clear during follow-up after radioiodine treatment resulted in hyperthyroidism.
“The independent association of mortality with serial measurements of free thyroxine during treatment provides a causative link between poor outcome and control of hyperthyroidism, and the association of mortality with atrial fibrillation at presentation highlights the central importance of this dysrhythmia in contributing to poor outcome,” Kristien Boelaert, MD, PhD, MRCP, senior research fellow and endocrinologist at the University Hospitals Birmingham NHS Foundation Trust, and colleagues wrote.
They conducted a prospective, observational, population-based study of 1,036 patients assigned to a single specialist clinic from 1989 to 2003. Researchers aimed to determine whether mortality was associated with hyperthyroidism and how it varies with treatment or other factors. Patients were followed until 2012.
In 12,868 person-years of follow-up, 334 participants died vs. 290.6 deaths expected, given the number of person-years at risk (standardized mortality ratio [SMR]=1.15; 95% CI, 1.03-1.28). An increase in all-cause mortality mostly demonstrated an increase in circulatory deaths (SMR=1.20; 95% CI, 1.01-1.43), according to data.
Additionally, all-cause mortality increased as person-years increased during thionamide therapy (SMR=1.30; 95% CI, 1.05-1.61) and after radioiodine (131-I) treatment not associated with hypothyroidism (SMR=1.24; 95% CI, 1.04-1.46).
Conversely, this was not the case during T4 replacement for 131-I–induced hypothyroidism (SMR=0.98; 95% CI, 0.82-1.18), researchers said. Within-cohort analysis comparing mortality during thionamide treatment showed a similar HR for all-cause mortality when 131-I did not result in hypothyroidism (HR=0.95; 95% CI, 0.70-1.29), but reduced mortality with 131-I–induced hypothyroidism (HR=0.70; 95% CI, 0.51-0.96).
Further data indicate a reduction in mortality associated with hypothyroidism was only observed in patients without significant comorbidities and other serious diseases. There was an independent association between mortality and atrial fibrillation at presentation (P=.02) and an increment of 10 pmol/L in serial free T4 concentration during follow-up (P=.009), researchers wrote.
Besides highlighting the significance of this potential risk, Boelaert and colleagues recommend physicians consider significant adverse events associated with antithyroid drugs, including agranulocytosis and propylthiouracil-induced hepatic failure.
Disclosure: The researchers report no relevant financial disclosures.
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