PARATHYROID FUNCTION IN CARDIAC TRANSPLANT PATIENTS - EVALUATION DURING PHYSICAL EXERCISE

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). Despite a tendency for initial Ca++ concentrations to be lower in the patients (P < 0.07), there were no significant differences between both groups either for pH or for Ca++. These results show that in the early stage of transplantation, the patients under immunosuppressive therapy have moderate hyperparathyroidism which precedes the serious complications of bone loss in long-term transplant patients.