Objectives: (1) to establish the relative level of osteoporotic fracture in the thyroid population compared to the general population, and (2) to establish whether osteoporotic fracture in patients receiving thyroxine was associated with plasma thyroid stimulating hormone (TSH) level or thyroxine dose.
Method: A database of clinical information from subjects with treated thyroid disease was linked to morbidity records describing all in-patient episodes of care due to osteoporotic fracture. Subjects were identified from a region of approximately 400,000 from January 1993 to December 2001. (1) Poisson regression was used to model relative fracture rate. (2) A Cox proportional hazards model was used to establish predictors of morbidity. Data were anonymised with permission obtained from the local ethics committee.
Results: There were 14,802 primary hypothyroid and 3,812 hyperthyroid patients. (1) After adjustment for age and sex, an increased rate of osteoporotic fracture was found for male primary hypothyroid patients (rate ratio 1.51 95% CI 1.132.01), and female hyperthyroid patients (RR 1.39; CI 1.191.62). (2) For subjects on thyroxine, females were at approximately twice the risk of osteoporotic fracture compared to males, whilst there was an approximate doubling in risk for every five years over the age of fifty. No association was found between low and suppressed TSH, however patients with high TSH were at increased risk (hazard ratio 1.41; CI 1.101.80) this was partly reduced by adjusting for drug coverage a measure of secondary compliance. Dose of thyroxine was not associated with fracture risk after adjustment for age and sex.
Conclusions: There is increased osteoporotic fracture in males with hypothyroidism and females with treated hyperthyroidism. Age and sex were both predictors of fracture in subjects on thyroxine. High TSH concentration in such patients but not thyroxine dose was associated with increased risk. High TSH was partly accounted for through poor compliance.