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Mechanisms of rapid bone loss following cardiac transplantation
P N Sambrook1, P J Kelly, D Fontana
1Bone and Mineral Research Division, Garvan Institute of Medical Research, St. Vincent's Hospital, Darlinghurst, NSW, Australia.
Abstract:
Rapid bone loss after orthoptic cardiac transplantation (OHTX) is a major problem; however, the mechanisms are poorly understood. To investigate these mechanisms we measured biochemical and hormonal indices of bone turnover serially in 25 patients (21 men, 4 women) after OHTX. Serum osteocalcin was reduced immediately post-OHTX (2.2 +/- 0.5 ng/ml) but rose significantly by 6 and 12 months (14.1 +/- 2.5 and 15.7 +/- 2.2 respectively). Bone resorption indices (urinary hydroxyproline/creatinine and calcium/creatinine ratios) were increased immediately post-OHTX but fell by 6 months. Serum testosterone was reduced in males but recovered towards normal values by 6-12 months. Regression analysis showed lumbar bone loss was predicted independently by the change in both serum osteocalcin and testosterone. The data suggest that bone loss post-OHTX is due to a combination of accelerated turnover and hypogonadism.
Insights
Orthoptic cardiac transplantation (OHTX) leads to rapid bone loss. This study reveals accelerated bone turnover and hypogonadism contribute to bone loss post-OHTX.
Area of Science:
- Endocrinology
- Orthopedics
- Cardiology
Background:
- Rapid bone loss is a significant complication following orthoptic cardiac transplantation (OHTX).
- The underlying mechanisms driving this bone loss remain poorly understood.
- Understanding these mechanisms is crucial for developing effective interventions.
Purpose of the Study:
- To investigate the biochemical and hormonal mechanisms contributing to bone loss after OHTX.
- To assess changes in bone turnover markers and hormone levels serially post-transplantation.
- To identify predictors of lumbar bone loss in OHTX patients.
Main Methods:
- Serial measurement of biochemical indices of bone turnover (serum osteocalcin, urinary hydroxyproline/creatinine, calcium/creatinine).
- Hormonal assessment, including serum testosterone levels in male patients.
- Regression analysis to correlate bone loss with biochemical and hormonal changes.
Main Results:
- Serum osteocalcin levels were initially reduced but significantly increased by 6 and 12 months post-OHTX.
- Bone resorption indices (urinary hydroxyproline/creatinine, calcium/creatinine) were elevated immediately post-OHTX, decreasing by 6 months.
- Reduced serum testosterone levels in males recovered towards normal by 6-12 months, independently predicting bone loss.
Conclusions:
- Bone loss post-OHTX is multifactorial, involving accelerated bone turnover and hypogonadism.
- Changes in serum osteocalcin and testosterone levels are key predictors of lumbar bone loss.
- These findings highlight the need for monitoring and managing bone health in OHTX recipients.