Papaleontiou M, Levine DA, Reyes-Gastelum D, et al. - Using data from the Veterans Health Administration, researchers conducted this retrospective cohort study to explore the connection between thyroid hormone treatment intensity and incidence of atrial fibrillation and stroke. Participants in the study were 733,208 thyroid hormone users aged ≥ 18 years with at least two thyroid-stimulating hormone measurements between thyroid hormone beginning and incident event or study conclusion (406,030 thyroid hormone users with at least two free T4 measurements). Exogenous hyper- and hypothyroidism were both linked to a higher risk of stroke, emphasizing the value of patient medication safety.