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During the past decade considerable progress has been made in the field of calcium metabolism associated with chronic renal failure. The main factor influencing the pathophysiology of calcium homeostasis is its dependence on parathyroid hormone and active vitamin D metabolites. Among several new diagnostic tools, and to establish the diagnosis of renal osteodystrophy, only the measurement of i-PTH activity has any clinical relevance. The main goal in treating renal osteodystrophy is the lowering of PTH activity by correcting hyperphosphatemia and administration of calcitriol given either orally or intravenously. Furthermore, the need to lower the calcium concentration in the dialysate during calcitriol treatment is demonstrated. The clinical significance of adynamic osteodystrophy is still unclear.

The pathogenesis of renal osteopathy is multifactorial. Disturbances in calcium-phosphorus metabolism leading to the development of secondary hyperparathyroidism, abnormalities in vitamin D and beta-2-microglobulin metabolism, and aluminum intoxication are the most important factors. In this overview the clinic, diagnostic and therapeutic procedures of the renal osteopathy are presented.

The effects of calcium and magnesium on parathyroid hormone release from eight adenomas causing primary hyperparathyroidism and six hyperplastic glands causing hypercalcemic secondary hyperparathyroidism were investigated in vitro using single cell suspensions from the respective tissue. We observed suppression of parathyroid hormone release with increasing concentrations of either cation. The quantitative hormone secretions of both adenomatous and hyperplastic glands was identical.

The effects of cryopreservation on in vitro secretion and on the survival rate of parathyroid cells were investigated, in order to find possible causes for the frequent failure of autologous, human parathyroid tissue. A reduction in the hormone secretion or an influence on the secretion could be excluded. The freezing procedure, however, leads to a partial necrosis of the tissue. Similarly good results, as in the replantation of fresh tissue, can be achieved by compensating the necrotic cells using more particles.

Renal and extra-renal clearance of 18F and 99mTc-EHDP were compared in the same individuals. The 18F space is twice that of 99mTc-EHDP, as is its renal clearance. 99mTc undergoes glomerular filtration, 18F is excreted by glomerular filtration and tubular secretion. Extraction rate was determined indirectly by a comparison with extra-renal clearance, and for patients without bone disease it was four times as high for 18F as it was for 99mTc-EHDP. In patients with secondary hyperparathyroidism extra-renal clearance is greatly increased. This is explained by an increased extraction rate, which may be different for the two substances.