Background: Over 5 million people in the United States are diagnosed with heart failure (HF) and many continue to be hospitalized for exacerbations of this disease. An estimated 20 million Americans have been diagnosed with some form of thyroid disease. Thyroid hormones significantly impact cardiac muscle functions and elevated levels of thyroxine (T4), as seen in hyperthyroidism (HT), can cause worsening of HF symptoms. We sought to examine the association between HT and exacerbation of systolic, diastolic or combined HF, which may lead to poorer prognosis and increased mortality.

Methods: We retrospectively evaluated national Hospital Corporation of America (HCA) Healthcare inpatient data and examined mortality (primary endpoint) and length of stay (LOS) (secondary endpoint) in patients hospitalized with HF with and without a concomitant diagnosis of HT.

Results: A total of N=55,031 cases of HF were reviewed. The presence of HT was not significantly associated with mortality (p = 0.24) nor the secondary endpoint, LOS (p = 0.32). Nonetheless, a significant difference (p = 0.005) in the distribution of sex among individuals with and without HT was noted, particularly with a higher percentage of females with HF having a concomitant diagnosis of HT. A significant difference in age (p = 0.004) between individuals with and without HT was also seen – a lower median age was seen in patients with HT. Additionally, we noted a significant difference in LOS (p = 0.04) between individuals with HT among patients with a cardiovascular comorbidity; these patients had a mean LOS of 6.33 days versus mean LOS of 5.31 days for patient without HT.

Conclusions: In our analysis, simultaneous diagnosis of HF and HT did not impact mortality; however, as the pathophysiology of HT can affect the symptoms of HF, further studies of this association are warranted.