Prevalence and risk of Vertebral Fractures in Primary Hyperparathyroidism: A nested case-control study.

Introduction Prevalence of vertebral fractures (VFx) in primary hyperparathyroidism (PHPT) remains uncertain. We aimed to estimate the prevalence of VFx, investigate potential risk factors associated with VFx and whether bone mineral density (BMD) differs between PHPT- and osteoporotic-patients with VFx. Methods Through the Danish National Patient Register, we identified patients diagnosed with PHPT between 2005-2015. The diagnosis was verified by reviewing biochemical findings and X-ray reports were reviewed by two investigators. Osteoporotic patients with VFx were identified from our outpatient clinic and matched on age and sex with PHPT patients with VFx. Results We identified 792 PHPT patients among whom spine X-ray was available from 588 patients. VFx were present in 122 (21%) patients and were equally frequent among sexes (77% females). Fractured patients were older (70 vs 63 yrs.) and had lower heights (163 vs 166 cm) compared to non-fractured patients (pall <0.02). After stratification by age-groups, the prevalence of VFx differed significantly between sexes (p < 0.01). Ionizedcalcium and PTH did not differ between groups. BMD at total hip and forearm were lower in fractured compared to non-fractured patients (p < 0.03 for both) after adjusting for age, sex and BMI. Compared with osteoporotic patients with VFx (N = 108), BMD at the lumbar spine was higher in PHPT patients with VFx (N = 108) (p < 0.01). This did not change by excluding patients with lumbar VFx (p < 0.01). Conclusion The severity of PHPT assessed by biochemistry does not seems to be associated with risk of VFx. Compared with osteoporosis; VFx seems to occur at a higher BMD in PHPT. This article is protected by copyright. All rights reserved.