Cross-national comparison of levothyroxine utilization in four developed countries

Abstract

Context: While hypothyroidism is prevalent globally, there may be considerable variation in the use of therapies to treat this condition. Aims: The aim was to examine temporal trends of levothyroxine utilization in Canada, Greece, Ireland and the United States. Settings and Design: A cross-sectional, population-based time series study was conducted to assess monthly utilization rates from January 1, 2005 to September 20, 2011, in Canada, Greece, Ireland and the United States. The primary outcome measure was the monthly rate of levothyroxine utilization for each country analyzed. Materials and Methods: Levothyroxine utilization data were obtained from IMS Health Inc., and temporal trends in monthly units dispensed per 1,000 population were examined. Statistical Analysis Used: Time series analysis was used to examine temporal trends in levothyroxine utilization. Results: While levothyroxine utilization rates increased over time in all regions, considerable differences were noted between regions - 80% relative difference in average monthly utilization between the highest (Greece - 1,664 units/1,000 population) and lowest (Ireland - 925 units/1,000 population) utilization countries was observed. We observed a nearly 3.5-fold difference in utilization of moderate-to-high strength doses (100 μg+) of levothyroxine between the countries examined. Conclusions: We noted considerable regional variation in the use of levothyroxine. Further research is needed to understand the drivers of these variations in utilization rates.