Although many cardiovascular risk factors are known, the persistent public health impact of cardiovascular disease mandates a more complete understanding of novel risk factors. Thyroid hormone treatment is widespread, with levothyroxine prescriptions consistently among the top 3 of all prescription medications in the United States in the past decade. However, up to 50% of patients who receive thyroid hormone treatment may exhibit exogenous hyperthyroidism or hypothyroidism (ie, have thyrotropin levels below or above the reference range, respectively). The associations of long-term exogenous hyperthyroidism and hypothyroidism with clinical outcomes have recently been investigated. Serum thyrotropin concentrations outside the euthyroid range correlated with increased cardiovascular risk and all-cause mortality among patients who received thyroid hormone treatment for hypothyroidism; however, studies focusing specifically on the association between the intensity of thyroid hormone treatment and cardiovascular mortality are lacking. A novel analysis aiming to evaluate the association between the intensity of thyroid hormone treatment and cardiovascular mortality (ie, death from cardiovascular causes, including myocardial infarction, heart failure, or stroke) based on a nationwide, population-based cohort was published on May 12, 2022 in JAMA Network Open.
This retrospective cohort study used data on 705 307 adults who received thyroid hormone treatment from the Veterans Health Administration Corporate Data Warehouse between January 1, 2004, and December 31, 2017, with a median follow-up of 4 years (IQR, 2-9 years). Two cohorts were studied: 701 929 adults aged 18 years or older who initiated thyroid hormone treatment with at least 2 thyrotropin measurements between treatment initiation and either death or the end of the study period, and, separately, 373 981 patients with at least 2 free thyroxine (FT4) measurements. Data were merged with the National Death Index for mortality ascertainment and cause of death.
The majority of patients (88.7%) were men, and the median age was 67 years (IQR, 57-78 years). Overall, 75 963 patients (10.8%) died of cardiovascular causes. After adjusting for age, sex, traditional cardiovascular risk factors, and previous cardiovascular disease or arrhythmia, patients with exogenous hyperthyroidism (eg, thyrotropin levels, <0.1 mIU/L: adjusted hazard ratio [AHR], 1.39; 95% CI, 1.32-1.47; FT4 levels, >1.9 ng/dL: AHR, 1.29; 95% CI, 1.20-1.40) and patients with exogenous hypothyroidism (eg, thyrotropin levels, >20 mIU/L: AHR, 2.67; 95% CI, 2.55-2.80; FT4 levels, <0.7 ng/dL: AHR, 1.56; 95% CI, 1.50-1.63) had increased risk of cardiovascular mortality compared with individuals with euthyroidism. These findings emphasize the importance of maintaining euthyroidism to decrease cardiovascular risk and death among patients receiving thyroid hormone treatment.
Reference: https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2792219
