Prevalence of hypothyroidism in Finland--a nationwide prescription study.

PURPOSE

The aim of this study was to estimate the 1-year prevalence of levothyroxine-treated hypothyroidism in Finland.

METHODS

Data on all individuals who had regularly purchased levothyroxine sodium tablets during 2007 were retrieved from the nationwide Finnish Drug Prescription Database. The prevalence rates and 95% confidence intervals were calculated per 100 individuals assuming a Poisson distribution.

RESULTS

In total, 189,027 individuals (84% female) were identified as using levothyroxine tablets, which translated into a 1-year prevalence of hypothyroidism of 3.6%. The disease was notably more common in females (5.9%) than in males (1.2%), with a gender prevalence rate ratio (PRR) of 4.5. Prevalence increased with age. A comparison of five university hospital districts revealed that the prevalence rates were fairly stable regionally, with the lowest rate being 3.1% and the highest 4.4%; the regional PRR was 1.3.

CONCLUSIONS

To the best of our knowledge, this nationwide prescription study includes the largest population of reported levothyroxine users to date. This comprehensive data justifies estimating the gender- and age-specific prevalence of hypothyroidism in Finland.