FRI526 Geographic Trends In Thyroid Hormone Prescribing In The US: 2010 - 2020

Disclosure: M.D. Ettleson: None. N. Laiteerapong: None. W. Wan: None. A.C. Bianco: Consulting Fee; Self; Abbvie, Acella, Synthonics, Thyron, Madrigal. Introduction: Levothyroxine (LT4) is the first line treatment of hypothyroidism. However, some clinical guidelines suggest a trial of adding triiodothyronine (T3) therapy if LT4 monotherapy does not adequately resolve symptoms despite a normal thyrotropin (TSH) level. It is unknown how patterns of thyroid hormone (TH) prescribing (LT4 vs T3-containing therapy) differ across the US. Methods: We conducted a cross-sectional study of TH prescription data from a large, US-based claims database from January 1, 2010 to December 31, 2020. TH type (LT4, liothyronine [LT3], or desiccated thyroid extract [DTE]), geographic, and clinical data were collected. Only patients with a new TH prescription and a diagnosis of hypothyroidism were included. The study population was subdivided into 4 TH treatment classes: 1) LT4 monotherapy, 2) LT3 therapy with or without LT4, 3) DTE therapy with or without LT4, and 4) other. Statewide physician density and urban-rural classification were the primary geographic covariates analyzed. Other covariates included in the analytical models were age, sex, comorbidities, and co-prescribed medications. Results: A total of 524,818 adult patients accounted for 537,594 new TH prescriptions over the 11 year study period. Of the total population, 89.0% received LT4 monotherapy, 8.8% received DTE therapy, and 2.0% received LT3 therapy. The proportion of patients receiving DTE increased from 5.4% to 10.2% during the study period. DTE and LT3 prescriptions were not uniformly distributed throughout the US, with higher rates in the West and South regions. Residence in a state with higher endocrinologist density (3.0/100k population) was associated with a decreased likelihood of receiving LT3 or DTE therapy (adjusted OR 0.33, 95% CI [0.20 – 0.55], p <0.001; adjusted OR 0.18, 95% CI [0.08 – 0.41], p <0.001, respectively). Residence in large central metro zones was associated with an increased likelihood of receiving LT3 or DTE therapy (adjusted OR 1.32, 95% CI [1.22 – 1.42]; p <0.001; adjusted OR 1.05, 95% CI [1.01 – 1.10], p = 0.008, respectively). Conclusions: There do appear to be geographic disparities in the patterns of TH prescribing in the US. Differences in access to endocrine care may contribute to these disparities. Also, patients in more urban zones were more likely to receive LT3 or DTE therapies. Further investigation is necessary to understand the patient and physician-level factors underlying the geographic disparities identified. Presentation: Friday, June 16, 2023