M Fleseriu1, A A Licata. 1. Department of Endocrinology, Diabetes and Metabolism, Cleveland Clinic, Desk A53, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
Abstract
INTRODUCTION: Bone metabolism disturbances following renal transplantation (RT) are complex and multifactorial in origin. Abnormalities in 1,25-dihydroxyvitamin D levels in RT patients under treatment at our Bone Center prompted this retrospective study. METHODS: Parameters of vitamin D metabolism were compared in RT patients and a cohort of patients with primary hyperparathyroidism (PHTP) who mimicked the hyperparathyroid state of the RT patients. Thirty-one RT recipients (from 300 reviewed) matched our inclusion criteria with a stable graft function for more than 1 year and a glomerular filtration rate (GFR) >50 mL/min per 1.73 m(2) (Group A); these were compared with 42 consecutive patients with PHTP who had been referred to the same Bone Center for treatment for over 1 month (Group B). Statistical analysis included the chi-square or Fisher's exact tests for categorical data and the Wilcoxon rank sum test for quantitative measures. RESULTS: The mean (+/-SD) 1,25-dihydroxyvitamin D level was significantly lower (p < 0.001) in Group A patients (29.8 +/- 16.2) than in Group B patients (70.2 +/- 25.9) despite non-significant differences in the levels of parathyroid hormone (PTH) (mean: 184.0 vs.101.1;p < 0.29), phosphorus (mean: 3.2 vs. 3.1; p < 0.3) and 1,25-vitamin D (mean: 19.5 vs. 25.2; p < 0.06). Group A patients had lower levels (p < 0.05) of mean serum calcium and calculated GFR (9.3 mg/dL, 65.7 mL/min) than Group B patients (10.6 mg/dL, 97.6 mL/min). 1,25-Dihydroxyvitamin D significantly correlated with calcium (p < 0.001), 25-vitamin D (p < 0.005) and GFR (p < 0.001) in both groups, but there was a notable lack of association between 1,25-dihydroxyvitamin D and PTH (p < 0.64) or phosphorus (p < 0.26) in Group A patients. In this group, 1,25-dihydroxyvitamin D was not influenced by the type of immunosuppresion regimen (p < 0.06), use of biphosphonates (p < 0.73), presence of diabetes (p < 0.59), menopause in women (p < 0.08), season (p < 0.43) or race (p < 0.31). Our data indicate that 1,25-dihydroxyvitamin D metabolism remains disturbed for a considerable time after successful RT, with the result that the level of 1,25-dihydroxyvitamin D in RT patients is lower despite physiological signals that should stimulate its production. Our analysis of many clinical variables was unable to elucidate the underlying mechanism(s) for this disturbance. CONCLUSION: Successful RT may not produce appropriate levels of 1,25-dihydroxyvitamin D commensurate to the elevated levels of PTH. This abnormality along with sustained hyperparathyroidism may contribute to bone loss following transplantation.
INTRODUCTION: Bone metabolism disturbances following renal transplantation (RT) are complex and multifactorial in origin. Abnormalities in 1,25-dihydroxyvitamin D levels in RT patients under treatment at our Bone Center prompted this retrospective study. METHODS: Parameters of vitamin D metabolism were compared in RT patients and a cohort of patients with primary hyperparathyroidism (PHTP) who mimicked the hyperparathyroid state of the RT patients. Thirty-one RT recipients (from 300 reviewed) matched our inclusion criteria with a stable graft function for more than 1 year and a glomerular filtration rate (GFR) >50 mL/min per 1.73 m(2) (Group A); these were compared with 42 consecutive patients with PHTP who had been referred to the same Bone Center for treatment for over 1 month (Group B). Statistical analysis included the chi-square or Fisher's exact tests for categorical data and the Wilcoxon rank sum test for quantitative measures. RESULTS: The mean (+/-SD) 1,25-dihydroxyvitamin D level was significantly lower (p < 0.001) in Group A patients (29.8 +/- 16.2) than in Group B patients (70.2 +/- 25.9) despite non-significant differences in the levels of parathyroid hormone (PTH) (mean: 184.0 vs.101.1;p < 0.29), phosphorus (mean: 3.2 vs. 3.1; p < 0.3) and 1,25-vitamin D (mean: 19.5 vs. 25.2; p < 0.06). Group A patients had lower levels (p < 0.05) of mean serum calcium and calculated GFR (9.3 mg/dL, 65.7 mL/min) than Group B patients (10.6 mg/dL, 97.6 mL/min). 1,25-Dihydroxyvitamin D significantly correlated with calcium (p < 0.001), 25-vitamin D (p < 0.005) and GFR (p < 0.001) in both groups, but there was a notable lack of association between 1,25-dihydroxyvitamin D and PTH (p < 0.64) or phosphorus (p < 0.26) in Group A patients. In this group, 1,25-dihydroxyvitamin D was not influenced by the type of immunosuppresion regimen (p < 0.06), use of biphosphonates (p < 0.73), presence of diabetes (p < 0.59), menopause in women (p < 0.08), season (p < 0.43) or race (p < 0.31). Our data indicate that 1,25-dihydroxyvitamin D metabolism remains disturbed for a considerable time after successful RT, with the result that the level of 1,25-dihydroxyvitamin D in RT patients is lower despite physiological signals that should stimulate its production. Our analysis of many clinical variables was unable to elucidate the underlying mechanism(s) for this disturbance. CONCLUSION: Successful RT may not produce appropriate levels of 1,25-dihydroxyvitamin D commensurate to the elevated levels of PTH. This abnormality along with sustained hyperparathyroidism may contribute to bone loss following transplantation.
Authors: J Toro; M A Gentil; R García; M A Pérez-Valdivia; E García Avellano; G R Algarra; P Pereira; F González-Roncero; J Mateos Journal: Transplant Proc Date: 2005-04 Impact factor: 1.066
Authors: K Falkiewicz; B Bidzińska; M Demissie; M Boratyńska; S C Zmonarski; K Tworowska; M Klinger; A Milewicz; D Patrzałek Journal: Transplant Proc Date: 2005-03 Impact factor: 1.066
Authors: H U Stempfle; C Werner; S Echtler; U Wehr; W A Rambeck; U Siebert; P Uberfuhr; C E Angermann; K Theisen; R Gärtner Journal: Transplantation Date: 1999-08-27 Impact factor: 4.939