Thyroid over-replacement may increase atrial fibrillation, stroke risks
CHICAGO— Among a large cohort of adults prescribed thyroid hormone replacement therapy, those with low thyroid-stimulating hormone levels had more atrial fibrillation and strokes, according to study data presented at the American Thyroid Association annual meeting.
“Our study provides new insights on the risks of atrial fibrillation and stroke in patients being treated with exogenous thyroid hormone,” Maria Papaleontiou, MD, assistant professor of internal medicine in the division of metabolism, endocrinology and diabetes at the University of Michigan, told Endocrine Today. “We found that despite controlling for known cardiovascular risk factors, such as smoking, hypertension, etc, low serum TSH was associated with both incident atrial fibrillation and stroke.”
Papaleontiou and colleagues analyzed data from the Corporate Data Warehouse of the Veterans Health Administration collected between 2004 and 2017 on 756,555 adults who were prescribed thyroxine alone or T4 plus liothyronine. Patients with thyroid cancer and those with medications that alter thyroid function tests, such as amiodarone, were excluded
All patients had at least two available TSH measurements, and 29% of them had at least one measurement less than 0.5 mIU/L, indicating over-replacement, according to Papaleontiou. Among the entire cohort, 10.5% had atrial fibrillation and 2.4% experienced a stroke.
Using multivariable generalized linear mixed-effects models, the researchers found that incident atrial fibrillation was statistically significantly associated with lower vs. higher TSH level (OR = 0.97; 95% CI, 0.96-0.97), older vs. younger age (e.g. age ≥85 years: OR = 9.46; 95% CI, 8.98-9.96 compared to age 18-49) and cardiovascular risk factors such as hypertension (OR = 1.73; 95% CI, 1.69-1.78). Similarly, stroke was significantly associated with lower TSH (OR = 0.98; 95% CI, 0.97-0.99) even when adjusting for other cardiovascular risk factors including history of prior atrial fibrillation.
“Low TSH was independently associated with incident stroke in thyroid hormone users, even when controlling for prior history of atrial fibrillation, the most common mechanism thought to lead to stroke in hyperthyroidism,” Papaleontiou said. “This suggests that there may be additional mechanisms leading to increased risk of stroke in patients who are over-replaced with thyroid hormone.” – by Jill Rollet
Papaleontiou, M. Oral Abstract 12. Presented at: 89th Annual Meeting of the American Thyroid Association; Oct. 30-Nov. 3, 2019; Chicago.
Disclosure: Papaleontiou reports no relevant financial disclosures.