Patients receiving levothryxine more likely to lose muscle mass, exhibit higher OA risk
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Key takeaways:
- Patients receiving levothyroxine were more likely to lose muscle mass in their quadriceps.
- Levothyroxine use was also associated with a higher risk for knee osteoarthritis.
Patients treated with levothroxine are more likely to experience a reduction in quadricep muscle mass, which may increase the risk for knee osteoarthritis, according to data published in Arthritis Research & Therapy.
“Levothyroxine, the primary treatment for hypothyroidism, prescribed for more than 7% of Americans, is one of the most commonly used medications in the USA,” Bahram Mohajer, MD, MPH, of Johns Hopkins University, and co-authors wrote.
“Using a dual-energy X-ray analysis scan, previous work has shown an association between levothyroxine therapy and changes in body composition primarily via a decrease in muscle and lean body mass but not fat or bone mass,” they added. “... No prior work has investigated the association between levothyroxine use and thigh muscles’ volume and function.”
To investigate the connection between levothyroxine (Levoxyl, Pfizer) and thigh muscle biomarkers in patients at risk for developing knee OA, Mohajer and colleagues analyzed data from the Osteoarthritis Initiative. The researchers included knees belonging to patients in the incident Osteoarthritis Initiative cohort who were without radiographic knee OA. Those who did not have exposure to OA due to the perceived lack of incidence risk were excluded.
Patients were assessed at baseline and during annual follow-up visits regarding the therapies they were receiving, specifically the use of levothyroxine. Additionally, Mohajer and colleagues used quantitative biomarkers to assess the size and composition of patients’ thigh muscle groups. Outcomes were radiographic and symptomatic knee OA during follow up in patients who demonstrated a Kellgren-Lawrence grade of less than 2 at baseline.
The analysis included a total of 1,043 matched thighs and knees, consisting of 266 levothryoxine users and 777 patients who were not receiving levothyroxine. Overall, use of levothyroxine was associated with decreased quadriceps cross-sectional area (mean difference = –16.06 mm2 per year; 95% CI, –26.70 to –5.41). However, the drug did not have an impact on muscle composition. In addition, use of levothyroxine was linked to an increased risk for radiographic knee OA (HR = 1.78; 95% CI, 1.78-1.15) and symptomatic knee OA incidence (HR = 1.93; 95% CI, 1.19-3.13).
“This study showed that levothyroxine use may be associated with loss of quadriceps muscle mass, which may also partially mediate the increased risk of [knee OA (KOA)] radiographic and symptomatic incidence in these participants,” Mohajer and colleagues wrote. “Further trials and prospectively designed observational studies are certainly warranted to assess the role of underlying thyroid function as a potential confounder or effect modifier on muscle changes and KOA risk.”
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