A study published in JAMA Network Open stated that maintaining euthyroidism was critical for lowering cardiovascular risk and death in thyroid hormone treatment patients.

705 307 individuals were included in the study. At least two thyrotropin readings were seen among 701,929 patients and at least two FT4 measurements were found in 373,981 patients throughout the study period. The most common cause of death in the study population was cardiovascular disease, which included myocardial infarction, heart failure, and stroke.

75 963 patients died of cardiovascular causes. It was observed that  exogenous hyperthyroidism patients (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 exogenous hypothyroidism patients (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 a higher risk of cardiovascular death compared to people with euthyroidism.

The intensity of thyroid hormone treatment was linked to cardiovascular (CV) mortality in this study. Both exogenous hyperthyroidism and exogenous hypothyroidism were linked to an elevated risk of cardiovascular mortality. Hence, preserving euthyroidism was critical for lowering cardiovascular risk and death in thyroid hormone patients. (MedPage Today May 12, 2022), JAMA Netw Open 2022; DOI: 10.1001/jamanetworkopen.2022.11863.