Increased risk of stroke, atrial fibrillation in exogenous hyperthyroidism, hypothyroidism

Patients with exogenous hyperthyroidism or hypothyroidism have been found to be at increased risk of stroke and atrial fibrillation, according to the results of a retrospective observational cohort study published in the Journal of Clinical Endocrinology and Metabolism.

The data is from the Veterans Health Administration. Patients (N = 733,208) who took thyroid hormones between 2004 and 2017 were screened for stroke or atrial fibrillation.

The patients were divided into 4 cohorts. Those who had at least 2 measurements of thyroid stimulating hormone (TSH) were screened for atrial fibrillation (n = 643,687) or stroke (n = 663,809), and those who had at least 2 measurements of free thyroxine (T4) were examined for atrial fibrillation (n = 342,021) or stroke (n = 351,542).

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The overall rate of atrial fibrillation was 11.08% and the stroke rate was 6.32%. The patients tended to have a higher free T4 (adjusted odds ratio [aOR], 1.04; 95% CI 1.03-1.05) as TSH (aOR, 0.97; 95% CI, 0.96-0.97).

In the TSH and free T4 cohorts, an increased risk of atrial fibrillation was associated with older age; current or previous smoking; and high blood pressure, diabetes mellitus and cardiovascular comorbidities.

In the TSH and free T4 cohorts, an increased risk of stroke was associated with older age; current or previous smoking; Black and Hispanic Ethnicity; and the comorbidities of high blood pressure, diabetes mellitus, hyperlipidemia and atrial fibrillation.

In exogenous hyperthyroidism (e.g. low TSH[[[[<0.1 mlU/L] or high free T4 [>1.9 ng / dl]), there was an increased risk of 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 strokes (OR, low TSH: 1.33; 95% CI 1.24-1.43; high free T4: 1.17; 95% CI 1.06-1.30) .

5 years after a low TSH level was found, the risk of atrial fibrillation increased 3.8-fold and stroke increased 4.2-fold. After the finding of a high free T4, the risk of atrial fibrillation and stroke increased by 4.6 and 2.2 times, respectively.

In exogenous hypothyroidism (e.g. high TSH [>5.5 mlU/L] or low free T4 [<.07 ng/dL]), there was an increased risk of 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).

5 years after a high TSH finding, the risk of atrial fibrillation increased 1.8 times and stroke 3.6 times. After finding a low free T4, the risk of stroke increased 3.5-fold.

Similar results were observed in the cohort of people aged 65 years and older.

These results may not be generalizable to women as only a few women (<15%) were included in this study.

These data showed that both exogenous hyperthyroidism and hypothyroidism were associated with an increased risk of stroke and atrial fibrillation.

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Papaleontiou M, Levine DA, Reys-Gastelum D, Hawley ST, Banerjee M, Haymart MR. Thyroid hormone therapy and stroke. J Clin Endocrinol Metab. Published online on June 17, 2021. doi: 10.1210 / clinem / dgab444

This article originally appeared on Endocrinology Advisor