Exogenous hyper-, hypothyroidism up risk of stroke

Both exogenous hyper- and hypothyroidism may increase the risk of incident stroke, according to a study, which notes the importance of patient medication safety.

This retrospective cohort study sought to determine the association of thyroid hormone treatment intensity with the incidence of atrial fibrillation (AF) and stroke. The authors used data from the Veterans Health Administration between 2004 and 2017, with a median follow-up of 59 months.

A total of 733,208 users of thyroid hormone therapy aged ≥18 years with at least two thyroid stimulating hormone (TSH) measurements between thyroid hormone initiation and incident event (AF or stroke) or study conclusion (406,030 thyroid hormone users with at least two free thyroxine [T4] measurements) participated in the study.

Some 71,333 out of 643,687 participants (11.08 percent) developed incident AF and 41,931 of 663,809 (6.32 percent) stroke.

Multivariable analyses that controlled for factors such as age, sex, and prior history of AF revealed that low TSH or high free T4 levels (ie, exogenous hyperthyroidism; eg, TSH <0.1 mIU/L: odds ratio [OR], 95 percent confidence interval [CI], 1.24–1.43; free T4 >1.9 ng/dL: OR, 1.17, 95 percent CI, 1.17, 95 percent CI, 1.06–1.30) and high TSH or low free T4 levels (ie, exogenous hypothyroidism; eg, TSH >5.5 mIU/L: OR, 1.29, 95 percent CI, 1.26–1.33; free T4 <0.7 ng/dL: OR, 1.29, 95 percent CI, 1.22–1.35), compared with euthyroidism (TSH >0.5–5.5 mIU/L and free T4 0.7–1.9 ng/dL), correlated with higher stroke incidence.

Notably, the risk of developing AF and stroke accumulated over time for both patients with exogenous hyper- and hypothyroidism.

“Stroke is a leading cause of death and disability and there is a need to identify modifiable risk factors,” the authors said.