Patients with exogenous hyperthyroidism or hypothyroidism were found to be at increased risk for incident stroke and atrial fibrillation, according to the results of an observational, retrospective cohort study published in The Journal of Clinical Endocrinology and Metabolism.
Data were sourced from the Veterans Health Administration. Patients (N=733,208) who were using thyroid hormones between 2004 and 2017 were assessed for incident stroke or atrial fibrillation.
Patients were subdivided into 4 cohorts. Those who had at least 2 thyroid-stimulating hormone (TSH) measurements were evaluated for atrial fibrillation (n=643,687) or stroke (n=663,809), and those who had at least 2 free thyroxine (T4) measurements were evaluated for atrial fibrillation (n=342,021) or stroke (n=351,542).
The overall rate of atrial fibrillation was 11.08% and stroke was 6.32%. Patients were more likely to have higher free T4 (adjusted odds ratio [aOR],1.04; 95% CI, 1.03-1.05) than TSH (aOR, 0.97; 95% CI, 0.96-0.97).
For atrial fibrillation, among the TSH and free T4 cohorts, increased risk was associated with older age; current or former smoking; and hypertension, diabetes mellitus, and cardiovascular disease comorbidities.
For stroke, among the TSH and free T4 cohorts, increased risk was associated with older age; current or former smoking; Black and Hispanic ethnicity; and the comorbidities of hypertension, diabetes mellitus, hyperlipidemia, and atrial fibrillation.
For exogenous hyperthyroidism (eg, low TSH [<0.1 mlU/L] or high free T4 [>1.9 ng/dL]), there was increased risk for atrial fibrillation (OR, low TSH: 1.31; 95% CI, 1.24-1.38; high free T4: 1.36; 95% CI, 1.26-1.47) and stroke (OR, low TSH: 1.33; 95% CI, 1.24-1.43; high free T4: 1.17; 95% CI, 1.06-1.30).
At 5 years after a finding of low TSH, the risk for incident atrial fibrillation increased by 3.8-fold and stroke by 4.2-fold. After a finding of high free T4, the risk for incident atrial fibrillation and stroke increased by 4.6-fold and 2.2-fold, respectively.
For exogenous hypothyroidism (eg, high TSH [>5.5 mlU/L] or low free T4 [<.07 ng/dL]), there was increased risk for atrial fibrillation (OR, high TSH: 1.13; 95% CI, 1.10-1.15) and stroke (OR, high TSH: 1.29; 95% CI, 1.29-1.33; low free T4: 1.29; 95% CI, 1.22-1.35).
At 5 years after a finding of high TSH, the risk for incident atrial fibrillation increased by 1.8-fold and stroke by 3.6-fold. After a finding of low free T4, the risk for incident stroke increased by 3.5-fold.
Similar results were observed among the cohort of individuals aged 65 years and older.
These findings may not be generalizable for women because few women were included (<15%) in this study.
These data indicated that both exogenous hyperthyroidism and hypothyroidism were associated with increased risk for stroke and atrial fibrillation.
Papaleontiou M, Levine DA, Reys-Gastelum D, Hawley ST, Banerjee M, Haymart MR. Thyroid hormone therapy and incident stroke. J Clin Endocrinol Metab. Published online June 17, 2021. doi:10.1210/clinem/dgab444