Levothyroxine Use Linked To Muscle Mass Loss And Increased Risk Of Knee Osteoarthritis

Patients receiving levothyroxine, the primary treatment for hypothyroidism, may be at higher risk of experiencing muscle mass loss in their quadriceps and an increased likelihood of developing knee osteoarthritis (OA), according to a recent study published in Arthritis Research & Therapy. Levothyroxine is one of the most commonly prescribed medications in the United States, with over 7% of Americans using it.

Researchers Mohajer B. and team from Johns Hopkins University analyzed data from the Osteoarthritis Initiative to investigate the association between levothyroxine use and thigh muscle biomarkers in patients at risk of developing knee OA. The study included knees of patients from the incident Osteoarthritis Initiative cohort without radiographic knee OA at

baseline. Patients who did not have exposure to OA were excluded.

Using dual-energy X-ray analysis scans, the researchers found a connection between levothyroxine therapy and a decrease in quadriceps cross-sectional area, indicating muscle mass loss in the thighs. However, the drug did not appear to impact muscle composition. Furthermore, levothyroxine use was associated with an increased risk of radiographic knee OA and symptomatic knee OA incidence during the follow-up period.

● According to the analysis of 1,043 matched thighs and knees, involving 266 levothyroxine users and 777 non-users, the use of levothyroxine was associated with a decrease in quadriceps cross-sectional area.

● On average, there was a reduction of 16.06 mm2 per year (95% CI: -26.70 to -5.41) in individuals using levothyroxine.

● However, the drug did not show any significant impact on muscle composition.

● The study found that levothyroxine use was linked to an increased risk of radiographic knee osteoarthritis (HR = 1.78; 95% CI: 1.78-1.15) and symptomatic knee osteoarthritis incidence (HR = 1.93; 95% CI: 1.19-3.13).

The study's findings suggest that patients treated with levothyroxine may experience a reduction in quadricep muscle mass, which could potentially contribute to an increased risk of developing knee osteoarthritis. These findings are important as levothyroxine is widely prescribed, and the impact on muscle mass and knee OA risk had not been previously explored.

Further trials and prospectively designed observational studies are needed to evaluate the role of underlying thyroid function as a potential confounder or effect modifier in muscle changes and knee OA risk. Understanding the mechanisms underlying the association between levothyroxine use, muscle mass loss, and knee OA can help guide clinical management and potentially lead to interventions to mitigate the risk.

While this study sheds light on the association between levothyroxine use, muscle mass loss, and knee osteoarthritis, further research is necessary to fully understand the underlying mechanisms and to establish guidelines for the optimal management of patients on levothyroxine therapy. By addressing these knowledge gaps, healthcare professionals can

improve patient care and outcomes for individuals with hypothyroidism who are receiving levothyroxine treatment.

Reference:

Mohajer B, et al. Arthritis Res Ther. 2023;doi:10.1186/s13075-023-03012-y.