HOUSTON – Patients with surgically treated hyperthyroidism have a lingering elevation in cardiovascular risk that persists for at least 2 decades post thyroidectomy, according to a Finnish national study.
“This is the first study to show increased risk of hospitalization for cardiovascular disease after thyroid surgery. The elevated risk is sustained 20 years after surgery. This is in line with previous studies done in patients treated with radioactive iodine. Thus, it’s probably the disease rather than the treatment that affects the patient’s heart permanently,” said Dr. Saara Metso of Tampere (Finland) University Hospital.
At the annual meeting of the Endocrine Society, she presented a population-based cohort study involving 4,334 hyperthyroid patients treated with thyroidectomy at any hospital in Finland during 1986-2007, along with 12,991 controls drawn from the general population.
The hospitalization rate for all cardiovascular causes during a median 10.5 years of follow-up was 240.5 per 10,000 person-years in the thyroidectomy group, compared with 206.2 per 10,000 person-years among controls.
Dr. Saara Metso
These rates translated into a highly significant 17% increased risk of cardiovascular hospitalization in patients after they have undergone thyroidectomy. The risk, however, was not elevated across the board for all forms of cardiovascular disease. For example, there was no significant difference between patients and controls in hospitalization rates for coronary artery disease, cerebrovascular disease, or heart failure. On the other hand, patients with surgically treated hyperthyroidism had a 27% greater rate of hospitalization for hypertension; a 51% increase in admissions for atrial fibrillation; and a 54% greater hospitalization rate for nonbacterial endo-, peri- and myocardial diseases, valvular diseases, and cardiomyopathy, she continued.
Dr. Metso noted that a recent meta-analysis of six studies featuring long-term follow-up of patients treated for hyperthyroidism showed that the subjects had a 19% increase in cardiovascular mortality relative to age- and sex-matched controls (Eur. J. Endocrinol. 2011;165:491-7). However, most of these patients had been treated with radioiodine. This is what prompted Dr. Metso and her coinvestigators to take a close look at surgically treated patients. The most common causes of their surgically treated hyperthyroidism were Graves disease in 48% of patients, multinodular goiter in 33%, and toxic adenoma in 6%.
Several audience members, while quick to praise the Finnish study as an important advance in the field, expressed a wish that Dr. Metso and her coworkers would have included radioiodine-treated hyperthyroid patients as a control group. Audience members also would have welcomed information on postthyroidectomy thyroid replacement hormone dosing to assess whether that could be a potential contributor to the observed increase in cardiovascular risk in thyroidectomized patients.
“It’s hard to understand how the adverse cardiovascular effects could last 2 decades after the end of hyperthyroidism,” one physician commented.
The Finnish national study was funded by the Pirkanmaa Hospital Research Fund. Dr. Metso reported having no financial conflicts.