SUN-395 Thyroid Function Testing Patterns in Newly Diagnosed Heart Failure

Abstract Disclosure: S. Joh: None. T.E. Villanueva: None. A. Nguyen: None. C. Huang: None. Introduction: Thyroid function evaluation is recommended in new-onset heart failure (HF). Guidelines from the American Association of Clinical Endocrinologists and the American Thyroid Association recommend that thyroid stimulating hormone (TSH) testing in the hospital setting should come with a high index of suspicion for thyroid dysfunction. Guidance for testing and treatment thresholds for thyroid dysfunction in patients hospitalized with new-onset HF is incomplete. This study aimed to examine TSH testing patterns and subsequent clinical management among patients hospitalized with new-onset HF. Methods: This is a retrospective study of adults hospitalized with new-onset HF between January 1, 2016 - June 30, 2024 within a large, multicenter, integrated health system. New-onset HF was defined as a hospitalization with a principal discharge diagnosis of HF by International Classification of Diseases code with no preceding HF diagnosis through 2008. Main exclusions included receipt of amiodarone, dronedarone, lithium, anti-thyroid, or thyroid replacement medication within 1 year prior to hospitalization and lack of follow-up data through 90 days after discharge. We examined TSH testing (normal range: 0.35-4 mcIU/mL) during hospitalization and outpatient (±90 days), concordance vs discordance between in-hospital vs outpatient measurements, and new thyroid replacement or anti-thyroid medication by 90 days after discharge. Results: Among 10,329 patients, the mean age was 72 (±14.8) years and 56% were male. The race/ethnicity of the cohort included 41% White, 31% Hispanic, 16% Black, 11% Asian-Pacific Islander, and 1% other/unknown. A total of 6254 (61%) had TSH testing within 90 days of hospitalization. Patients with HF with reduced ejection fraction (68%); atrial fibrillation (67%); and receiving anticoagulation (65%), guideline directed medical therapy beta blocker (65%), angiotensin receptor-neprilysin inhibitor (74%), mineralocorticoid receptor antagonist (67%), and sodium-glucose cotransporter 2 inhibitors (70%) had higher rates of TSH testing. Among patients tested, 3649 (58%) had at least one in-hospital TSH measurement, of which 966 (26%) also had at least one outpatient measurement. Within the 966 patients, 819 (85%) had concordant results between their in-hospital and outpatient measurements and 64 (7%) were initiated on new thyroid medication (51 thyroid replacement medication and 13 anti-thyroid medication). Conclusion: Thyroid testing among patients with new-onset HF was inconsistent in a real-world setting. Testing was more prevalent among patients with HF with reduced ejection fraction, atrial fibrillation, and those receiving guideline directed medical therapy. In-hospital TSH testing resulted in changes in management for a small subset of patients, though the clinical validity and implications of this is uncertain. Presentation: Sunday, July 13, 2025