Osteoporosis in adult survivors of adolescent cardiac transplantation may be related to hyperparathyroidism, mild renal insufficiency, and increased bone turnover

Background: Osteoporosis is common in adults who undergo cardiac transplantation. We hypothesized that adolescent cardiac transplant recipients also develop osteoporosis, which would persist into adulthood. Methods: We evaluated 9 adult survivors of adolescent cardiac transplantation, aged 21-32, in a cross-sectional, case-control study comparing bone mineral density, indices of mineral metabolism, and bone turnover markers. Results: Osteoporosis (Z score ≤ -2.0) was present in 56% of transplant recipients at the lumbar spine, 33% at the femoral neck, and 100% at the one-third radius. Subjects had mean bone mineral density Z scores of -2.3 ± 0.9 at the spine, -1.6 ± 0.7 at the femoral neck, and -3.2 ± 0.7 at the one-third radius, significantly lower than controls at all sites (p < 0.001). Serum creatinine and vitamin D metabolites were normal and did not differ between subjects and controls. Serum calcium was lower, blood urea nitrogen was elevated, and creatinine clearance tended to be lower in transplant recipients. Parathyroid hormone (PTH) levels were 3-fold higher in subjects than controls, and 75% of subjects had elevated PTH levels. Markers of bone turnover were significantly higher in subjects than controls. Conclusions: Adult survivors of adolescent cardiac transplantation have mild renal insufficiency, secondary hyperparathyroidism, and biochemical evidence of increased bone turnover. Osteoporosis is common in these patients, particularly at the one-third radius, a site sensitive to the catabolic effects of sustained excessive PTH secretion. We conclude that adult survivors of adolescent cardiac transplantation should be evaluated for hyperparathyroidism and osteoporosis.