Clinical Features and Outcomes of Myxedema Coma in Patients Hospitalized for Hypothyroidism: Analysis of the United States National Inpatient Sample.

BACKGROUND: Hypothyroidism is a common endocrine condition and chronic thyroid hormone deficiency is associated with adverse effects across multiple organ systems. In compensated hypothyroidism, however, patients remain clinically stable due to gradual physiologic adaptation. In contrast, the clinical syndrome of decompensated hypothyroidism referred to as myxedema coma (MC) is an endocrine emergency with high risk of morality. Because of its rarity, there are currently limited data regarding MC. This study analyzes the clinical features and hospital outcomes of MC compared to hypothyroid patients without MC (nonMChypo) in national United States (US) hospital data.

METHODS: A retrospective analysis of the National Inpatient Sample, a public database of inpatient admissions to non-federal hospitals in the US, 2016-2018, including adult patients with primary diagnosis of MC (ICD-10: E03.5) or nonMChypo (E03.0-E03.9, E89.0). Patient demographics, relevant clinical features, mortality, length of stay (LOS), and hospital costs were compared.

RESULTS: Of 18,635 patients hospitalized for hypothyroidism, 2,495 (13.4%) had a diagnosis of MC. Sex distribution and ethnicity/race were similar between patients with MC and nonMChypo, whereas MC was associated with older patient age (p=0.02), public insurance (p=0.01), and unhoused status (p=0.04). More admissions with MC occurred in winter compared to other seasons (p=0.01). The overall mortality rate for MC was 6.8% vs. 0.7% for nonMChypo (p<0.001), and MC was independently associated with in-hospital mortality after adjusted regression analysis (adjusted odds ratio = 9.92 [CI 5.69-17.28], p<0.001). Mean length of stay (LOS) ± standard deviation was 9.64 ± 0.73 days for MC vs. 4.62 ± 0.12 days for nonMChypo (p<0.001), and total hospital cost for MC was $21,768 ± $1,759 vs. $8,941 ± $276 for nonMChypo (p=0.07). In linear regression analyses, MC was an independent predictor of both increased LOS and total hospital costs.

CONCLUSION: In summary, myxedema coma remains a clinically significant diagnosis in the modern era, independently associated with high mortality and health care costs. This continued burden demonstrates a need for further efforts to prevent, identify, and optimize treatment for patients with myxedema coma.