Patients treated for hyperthyroidism or
hypothyroidism have an increase in frequency of some cardiovascular
disorders
(July 2006)
The background of the study. Patients with either
hyperthyroidism or hypothyroidism may have abnormal cardiovascular
function. Whether patients with either thyroid disorder who have
been treated have an increase in cardiovascular morbidity and mortality
and overall (all-causes) mortality is not known. In this study,
the frequency of these outcomes was determined in patients treated
for hyperthyroidism or hypothyroidism.
How the study was done. The study subjects were
all patients living in Tayside, Scotland, who had been treated for
hyperthyroidism or hypothyroidism between 1994 and 2001. Cases were
identified from physician, hospital, laboratory, and medication
records; a thyroid registry; and mortality records. The outcomes
studied were all-cause and cardiovascular mortality and cardiovascular
diseases, including ischemic heart disease (myocardial infarction,
angina), heart failure, and cerebrovascular disease. The frequency
of these events in the patients was compared with the frequency
in the general population.
The results of the study. During the study period,
3888 patients were treated for hyperthyroidism and followed for
21,190 patient-years; 772 were newly diagnosed during the study
period. For hypothyroidism, there were 15,889 patients followed
for 79,345 patient-years; 7904 were newly diagnosed. By 2001, the
prevalence of hyperthyroidism was 0.7 percent and that of hypothyroidism
2.9 percent.
There was no increase in all-cause mortality in the treated patients
with hyperthyroidism or hypothyroidism. There was an increase in
death from cardiovascular diseases in the treated patients with
hypothyroidism. Among the newly diagnosed patients, there was an
increase in cardiac-rhythm disorders in the treated patients with
hyperthyroidism, and small increases in death from cardiovascular
disease and in frequency of cardiovascular diseases, including ischemic
heart disease, heart failure, cardiac-rhythm disorders, and cerebrovascular
disease, in the treated patients with hypothyroidism.
The conclusions of the study. All-cause mortality
is not increased in patients with hyperthyroidism or hypothyroidism
who have been treated. The frequency of cardiac arrhythmias is increased
in treated patients with hyperthyroidism, and the frequency of some
cardiovascular diseases is increased in treated patients with hypothyroidism.
The original article. Flynn RW, MacDonald TM,
Jung RT, Morris AD, Leese GP. Mortality and vascular outcomes in
patients treated for thyroid dysfunction. J Clin Endocrinol Metab
2006;91:2159-64.
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