Determinants for Thyroid Hormone Replacement Therapy in Subclinical Hypothyroidism: A Multicenter Electronic Health Records-Based Study.

Background: The frequency and factors associated with thyroid hormone replacement therapy among patients with subclinical hypothyroidism (SCH) remain uncertain. Methods: In this electronic health records-based observational cohort study, we included adults diagnosed with SCH from four academic centers (the United States and Mexico) from January 1, 2016, to December 31, 2018. We aimed to identify the determinants of thyroid hormone replacement therapy for SCH and the frequency of treated SCH. Results: A total of 796 patients (65.2% women) had SCH, and 165 (20.7%) were treated with thyroid hormone replacement therapy. The treated group was younger [51.0 (standard deviation {SD} 18.3) vs. 55.3 (SD 18.2) years, p = 0.008] and had a higher proportion of women (72.7% vs. 63.2%, p = 0.03) compared with the untreated group. Only 46.7% of patients in the treated group and 65.6% in the untreated group had confirmatory thyroid function tests (TFTs) before the decision to start thyroid hormone replacement therapy was made. There was no difference in the frequency of thyroid autoimmunity evaluation, but a positive thyroid autoimmunity test was more frequent in the treated group compared with the untreated group (48.2% vs. 20.3%, p < 0.001). In a multivariable logistic regression model, female sex (odds ratio [OR] = 1.71 [CI 1.13-2.59], p = 0.01) and index thyrotropin (TSH) level (OR = 1.97 [CI 1.56-2.49], p < 0.001 for every SD [2.75 mIU/L] change) were associated with higher odds of treatment. Conclusions: Among patients with SCH, female sex and index TSH level were associated with higher odds of treatment. Moreover, in our population, the decision to treat or not to treat SCH was often based on only one set of abnormal TFTs, and thyroid autoimmunity assessment was underused.

Subacute Thyroiditis and Heart Failure in a Patient Presenting With COVID-19.

A 67-year-old male was admitted with shortness of breath and diarrhea. His COVID-19 polymerase chain reaction test was positive, and he was found to be in acute heart failure. Troponin levels were elevated, echocardiogram showed ejection fraction of 24%, and his electrocardiogram was normal. Inflammatory markers were elevated. Further testing revealed suppressed thyroid-stimulating hormone and elevated free thyroxine (T4). Differential diagnosis at this point included possible myocarditis from the viral illness, exacerbation of heart failure from the viral infection or from thyrotoxicosis was considered. Patient's heart failure improved with initiation of heart failure therapies; however, biochemically, his thyroid function tests (TFTs) did not improve, despite empiric methimazole. Thyroid antibody tests were unremarkable. Thyroid ultrasound showed mildly enlarged thyroid gland with no increased vascularity and 5-mm bilateral cysts. Thyroid dysfunction was attributed to subacute thyroiditis from COVID-19, methimazole was tapered, and prednisone was initiated. The patient's TFTs improved. With the ongoing COVID-19 pandemic, it is imperative that clinicians keep a broad differential in individuals presenting with heart failure, and obtaining baseline TFTs may be reasonable. Rapid treatment of the underlying thyroiditis is important in these patients to improve the cardiovascular outcomes. In our experience, steroid therapy showed a rapid improvement in the TFTs.