Mortality and vascular outcomes in patients treated for thyroid dysfunction

There are limited studies describing mortality and morbidity in patients treated for hyperthyroidism, and no data exist for people with treated hypothyroidism.

The objective of the study was to describe all-cause mortality and vascular mortality and morbidity in patients after treatment for hyperthyroidism and hypothyroidism.

This was a population-based cohort study from 1994 to 2001.

The study was conducted in Tayside, Scotland.

All patients were treated for thyroid dysfunction.

Event rates among patients with thyroid dysfunction were compared with rates in the general population. We measured standardized mortality ratio and standardized incidence ratio (SIR).

The primary outcome was all-cause mortality. The secondary outcome was serious vascular event, the composite end point of nonfatal myocardial infarction, nonfatal stroke, or vascular death.

There were 15,889 primary hypothyroid and 3,888 hyperthyroid patients. There were 3,116,719 patient-years of follow-up in 524,152 subjects in the general population. No increase was found in all-cause mortality or serious vascular events in patients with treated hypothyroidism or hyperthyroidism. Nonfatal ischemic heart disease [SIR 1.23, 95% confidence interval (CI) 1.10-1.36] and dysrhythmias (SIR 1.32, 95% CI 1.11-1.57) were increased in treated hypothyroidism when adjusted for age, sex, diabetic status, and previous vascular disease. In treated stabilized hyperthyroidism, only the risk of dysrhythmias was increased (SIR 2.71, 95% CI 1.63-4.24). Risk of heart failure or cerebrovascular disease was not increased in either patient group.

We found no increase in all-cause mortality in subjects with treated thyroid disease. However, there was increased risk of cardiovascular morbidity in patients with treated primary hypothyroidism and dysrhythmias in treated hyperthyroidism.