Use of Statins Among Patients Taking Levothyroxine: An Observational Drug Utilization Study Across Sites

Background Treatment with levothyroxine (LT4) that normalize serum TSH is expected to restore lipid metabolism. Methods Here we assessed statin utilization in LT4-treated patients through an observational drug utilization study in 3 sites: #1: 10,723 outpatients placed on LT4 during 2006-2019 identified from the Clinical Research Data Warehouse of the University of Chicago; #2: ∼1.4 million LT4 prescriptions prepared by primary care physicians during January-December 2018, identified from the AQVIA™ database of medical prescriptions in Brazil; #3: ~5.4 million patient interviews during 2009-2019, including ~0.32 million patients on LT4, identified from the Fleury Group database in Brazil. Results On Site #1, initiation of therapy with LT4 increased the frequency of statin utilization (19.1 vs 24.6%), which occurred ~1.5 years later (median 76 wks) and, among those patients that were on statins, increased intensity of treatment by 33%, despite normalization of serum TSH levels; on Site #2, after matching for sex and age, the frequency of statins prescription was higher for those patients using LT4: females: 2.1 vs 3.4% (OR: 1.656 [1.639 - 1.673]); males: 3.1 vs 4.4% (OR: 1.435 [1.409 - 1.462]); and, on Site #3, after matching for sex and age, the frequency of statins utilization was higher in those patients using LT4: females: 10 vs 18% (OR: 2.02 [2.00 - 2.04]); males: 15 vs 25% (OR: 1.92 [1.88 - 1.96]); all P-values were <.0001. Conclusion Prescription and utilization of statins were higher in patients taking LT4. The reasons for this association should be addressed in future studies.