Levothyroxine overprescribed in subclinical hypothyroidism patients: JAMA
USA: Levothyroxine is overused in patients with subclinical hypothyroidism during the past decade, according to a recent study in JAMA Internal Medicine.
Levothyroxine is one of the most commonly prescribed drug in the US. Previous studies have shown no clinically relevant benefits of levothyroxine replacement for thyroid-related symptoms or quality of life for nonpregnant adults with subclinical hypothyroidism.
To better understand levothyroxine use in the US over time, Juan P. Brito, and colleagues analyzed national data for commercially insured and Medicare Advantage enrollees.
For this purpose, the researchers conducted a retrospective analysis of deidentified administrative claims data linked with laboratory results from OptumLabs Data Warehouse, which includes commercially insured and Medicare Advantage enrollees throughout the US. It included adults (≥18 years of age) who newly filled levothyroxine prescriptions between January 1, 2008, and December 31, 2018, and who had a thyrotropin level measured within 3 months prior to levothyroxine initiation.
Descriptive statistics were used to characterize trends in thyrotropin levels and categories of thyroid function measured prior to levothyroxine initiation. In subsample with availability of thyrotropin and thyroxine levels, thyroid function was defined as overt hypothyroidism (elevated thyrotropin and low free or total thyroxine [FT4 or T4] levels), subclinical hypothyroidism (elevated thyrotropin and normal FT4 or T4 levels), and normal thyroid function (normal thyrotropin and FT4 or T4 levels).
Mild subclinical hypothyroidism (thyrotropin level of 4.5 mIU/L to <10 mIU/L with normal FT4 or T4), moderate subclinical hypothyroidism (thyrotropin level of 10-19.9 mIU/L), and severe subclinical hypothyroidism (thyrotropin level > 19.9 mIU/L) were also examined separately.
Between 2008 and 2018, 110 842 patients newly initiated levothyroxine treatment.
Key findings of the study include:
- The median thyrotropin level at treatment initiation did not significantly change: 5.8 mIU/L in 2008 to 5.3 mIU/L in 2018.
- In a subset of 58 706 patients with thyrotropin and FT4 or T4 levels available, levothyroxine was initiated for overt hypothyroidism (4948 [8.4%]), subclinical hypothyroidism (35 814 [61.0%]), and normal thyroid levels (17 944 [30.5%]).
- From 2008 to 2018, the proportion of adults with overt hypothyroidism increased (7.6% to 8.4%); the proportion with subclinical hypothyroidism did not change (59.3% to 65.7%); and the proportion with normal thyroid function did not change (32.9% to 26.2%).
- Among patients with subclinical hypothyroidism, the proportion with mild subclinical hypothyroidism (48.2% to 57.9%) and moderate subclinical hypothyroidism (8.5% to 6.4%) did not change significantly, and the proportion with severe subclinical hypothyroidism decreased (2.5% to 1.3%).
"In conclusion, these results suggest substantial overuse of levothyroxine during the entire duration of the study, suggesting opportunities to improve care," wrote the authors.
Reference:
The study titled, "Levothyroxine Use in the United States, 2008-2018," is published in JAMA Internal Medicine.
DOI: https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2781311
