Parathyroid function in cardiac transplant patients: evaluation during physical exercise

Abstract

The survival rate of heart transplant patients has increased considerably since the development of new immunosuppressive drugs. In the long term, however, cardiac transplantation results in a high incidence of osteoporosis which represents a major functional handicap. To examine whether patients in the early stages have impaired phosphocalcic metabolism, intact parathyroid hormone (PTH 1-84), native osteocalcin, ionized Ca++ and pH were measured at rest and during muscular exercises a dynamic test used to override circadian and ultradian PTH variations. A group of 12 patients receiving the usual immunosuppressive therapy, which is mainly an association of cyclosporin and prednisolone, and 8 sedentary control subjects performed a square-wave endurance test at the same relative intensity for 30 min. No patient had previous bone disease and the period since transplantation was 12.2 +/- 2.7 months. For the transplant patients, initial PTH concentrations and responses to exercise were higher (P < 0.01) compared to the control subjects with a dramatic increase after 10 min of recovery. From higher (P < 0.001) resting concentrations, osteocalcin further increased during exercise (P < 0.01) in the heart transplant group but not in the control subjects. In both groups pH showed the same time-course with a rapid fall during exercise (P < 0.05) and Ca++ concentrations increased during the exercise period. (P < 0.01 for patients; P < 0.05 for controls) with a significant fall in both groups after 10 min of recovery (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Moderate endurance training has no effect on the parathyroid function of heart transplant patients

“…As reported in a previous study (Brandenberger et al 1995), we have observed that basal concentrations and exercise-induced variations of PTH are signi®cantly higher in HTR than in healthy subjects. Whether this sustained, albeit moderate, hyperparathyroidism can contribute to long-term bone loss in HTR needs to be clari®ed.…”

“…This increase of Ca 2+ during exercise should theoretically induce a decrease of PTH. These simultaneous rises of Ca 2+ and PTH that we and other authors have observed (Nishiyama et al 1988;Henderson et al 1989;Ljunghall et al 1994;Salveson et al 1994;Brandenberger et al 1995) are paradoxical. The increase in PTH could be due at least partly to haemoconcentration.…”

“…These missing values were calculated using BMDP software (BMDP Statistical Software, Los Angeles, Calif., USA) prior to the variance analysis. For PTH, the area under the curve and the slope of the straight line plotted between the last exercise value and the ®rst recovery value [corresponding to the post-exercise peak of PTH as described in a previous work (Brandenberger et al 1995)] were calculated for each patient and compared using non-parametric tests. Results are expressed as the mean (SEM).…”

“…It has been shown that HTR under immunosuppressive therapy have moderate hyperparathyroidism, with a twofold increase in PTH resting levels as compared to control subjects (Brandenberger et al 1995). In these patients, a large increase of PTH was observed during exercise, the maximum occurring during the ®rst 10 min of recovery.…”