Bone mass and mineral metabolism in kidney transplant patients

A Rare Reason for Severe Hypocalcemia Following Kidney Transplant: Denosumab Treatment

Deviations of calcium, phosphate, parathyroid hormone, and vitamin D levels are the basis for the diagnosis of calcium-phosphate metabolism disorders. The plasma concentration of the biologically active form known as free calcium is regulated in a harmonious manner by its exchange in the bones and reabsorption by the kidneys. These steps take place under the control of parathyroid hormone and calcitriol. In the process of chronic kidney disease, the kidney cannot synthesize adequate calcitriol, and the resulting hypocalcemia and hyperphosphatemia cause the development of secondary hyperparathyroidism. Osteoporosis is a metabolic bone disease and is essentially the consequence of osteoclastogenesis-induced bone resorption that exceeds bone formation. Osteoporosis is common after kidney transplant. However, hypocalcemia following kidney transplant is rare. The hungry bone syndrome after parathyroidectomy is often responsible for this condition in the pretransplant period. Denosumab is a human monoclonal antibody developed against the receptor activator of nuclear factor kappa-B ligand (known as RANKL). Denosumab exerts an antiresorptive effect on bones by reducing differentiation into osteoclasts. It is an effective treatment option for osteoporosis in the general population. There is insufficient scientific data regarding the use of denosumab in kidney transplant patients. Here, we present the case of a kidney transplant recipient who developed severe hypocalcemia (serum calcium 4.7 mg/dL) after denosumab treatment for osteoporosis.

Abnormal bone and mineral metabolism in kidney transplant patients--a review

BACKGROUND/AIMS

Abnormal bone and mineral metabolism is common in patients with kidney failure and often persists after successful kidney transplant.

METHODS

To better understand the natural history of this disease in transplant patients, we reviewed the literature by searching MEDLINE for English language articles published between January 1990 and October 2006 that contained Medical Subject Headings and key words related to secondary or persistent hyperparathyroidism and kidney transplant.

RESULTS

Parathyroid hormone levels decreased significantly during the first 3 months after transplant but typically stabilized at elevated values after 1 year. Calcium tended to increase after transplant and then stabilize at the higher end of the normal range within 2 months. Phosphorus decreased rapidly to within or below normal levels after surgery and hypophosphatemia, if present, resolved within 2 months. Low levels of 1,25(OH)2 vitamin D typically did not reach normal values until almost 18 months after transplant.

CONCLUSION

This review provides evidence demonstrating that abnormal bone and mineral metabolism exists in patients after kidney transplant and suggests the need for treatment of this condition. However, better observational and interventional research is needed before advocating such a treatment guideline.