Session Information
Session Type: Abstract Submissions (ACR)
Background/Purpose:
Hyperparathyroidism is associated with reduced bone mineral density (BMD) and increased fracture risk. A previous study from this group has shown that bone loss in hyperparathyroidism occurs at both the lumbar spine and femoral neck.1 The condition is also associated with weight gain, and increased body mass index (BMI).2 A low BMI is a risk factor for BMD loss and osteoporosis, meaning that the higher BMI of hyperparathyroid patients may play a protective role against the increased BMD loss. This study aims to determine the relationship between BMD and BMI in hyperparathyroidism.
Methods: Using a nested case-control approach, a cohort of patients referred between 2004 and 2011 for a dual-energy x-ray absorptiometry scan with hyperparathyroidism as their main risk factor was identified. These were then age and gender matched with controls referred in the same time period with no indication for scanning. The odds of having osteoporosis were compared between cases and controls using a univariate logistic model. Simple differences in BMI were ascertained using students t-test, and sites of bone loss were ascertained by comparing BMD at two sites (L1-L4 vertebrae and the left femoral neck) between cases and controls. A multivariate logistic model was fitted to determine the interaction between BMI and bone loss in patients with hyperparathyroidism.
Results: 281 patients with hyperparathyroidism were identified, with 281 age and sex matched controls. There were 233 females (83%) in each group. Both groups had a mean age of 67.4 (SD 12.2). The odd of having osteoporosis in the hyperparathyroid group was 5.08 (95% CI 3.37-7.67). BMI was found to be significantly increased in the hyperparathyroid cohort (27.9 kg/m2 v 26.2 kg/m20 , mean difference of 1.612 kg/m2 (95% CI 0.782-2.442, p≤0.001). BMD was shown to also be significantly reduced in both the lumbar spine and the femoral neck, with maximal loss in the femur; mean BMD difference was 0.0345 g/cm2 in L1-L4 (95% CI 0.0003-0.0686, p≤0.05), and 0.0357 g/cm2 in the femoral neck(95% CI 0.0115-0.0598, p≤0.01). In the multivariate logistic model, a significant difference in BMD only persisted in the femoral neck , with an odds ratio of 6.86 (95% CI 1.37- 34.3, p≤0.05) for a lower BMD compared to an odds of 1.89 (95%CI 0.60,5.73) in the lumbar spine.
Conclusion: Hyperparathyroidism is shown to be associated with both a high BMI and an increased osteoporosis risk, with significantly reduced BMD at the femoral neck , but not the lumbar spine when adjusted for BMI. A reduced BMD in the presence of an increased BMI may be due to certain unique circumstances found in hyperparathyroidism, such as the presence of extra PTH-secreting cells in adipose tissue, or the sequestration of vitamin D in adipose tissue, which may lead to further PTH secretion and BMD loss.
1. Ann Rheum Dis. 2009;68:pp 0377.
2. A Meta-Analysis. Journal of Clinical Endocrinology & Metabolism. 2005;90(3):1525-30.
Disclosure:
C. Varley,
None;
A. Oldroyd,
None;
M. Bukhari,
None.
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