Influence of thyroid hormone therapy on the fracture rate - A claims data cohort study

It has been debated for years whether long-term thyroid hormone intake causes fractures. Not only have previous studies suffered from design limitations, they also reached contradictory conclusions. We investigated thyroid hormones (thyroxine) as a possible risk factor for fractures in a cohort of 6.7 million persons based on administrative data.

The database consists of anonymized settlement data of approximately 70 German statutory health insurances covering a time period of six years. All subjects aged 60 and above were included in the study; subjects with repeated thyroxine prescriptions were assigned to the exposure group; members without thyroxine prescriptions to the control group. Outcome was any incident fracture during a declared time period. In order to calculate fracture risk, we performed multivariate cox regression analyses to adjust for confounders.

Of 798 770 subjects fulfilling the inclusion criteria, 11.7% took thyroxine regularly and belong to the exposure group. The final cox regression showed that subjects taking thyroxine have a 6.3% higher risk (HR 1.063; CI 1.046-1.080, p=<.0001) than members of the control group.

The study supports the assumption that long term thyroxine intake leads to an increase in fracture risk among patients older than 60years. The findings have implications for long term thyroxine treatment.