What is the role of calcitriol (1,25-dihydroxyvitamin D) in the treatment of organ transplantation-related osteoporosis?

Updated: Jul 02, 2020
  • Author: Carmel M Fratianni, MD, FACE; Chief Editor: George T Griffing, MD  more...
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Answer

Kidney transplant and SPKT patients may continue to require posttransplant calcitriol for a brief period at doses lower than used during dialysis. [100] However, therapy must be individualized because a significant proportion of patients have persistent hyperparathyroidism, and calcitriol could worsen hypercalciuria and hypercalcemia.

Studies of oral calcitriol in solid organ transplantation have yielded mixed results. Spinal bone loss was not prevented with a low dose of calcitriol, 0.25 mcg/d or 0.5 mcg/48 h, in heart and kidney recipients. [69] In a single center in Spain, Toro et al described significant improvement at the femoral neck with alendronate and calcitriol administered late in the postoperative course. After approximately 13 months of treatment, a significant increase in BMD at the femoral neck was seen, although no improvement was seen at the level of the spine. [101]

Begun immediately after heart or lung transplantation, 6 months of calcitriol at 0.5 mcg daily versus cyclic etidronate was associated with spine and femur neck bone loss, although less than in an untreated historical control group. [102] This benefit clearly did not persist beyond 12–24 months.

In a randomized double blind 2-year study using higher doses of calcitriol at 0.5-0.75 mcg daily, beginning by 4 weeks posttransplantation, randomized to placebo or 12-24 months of calcitriol, similar spine bone loss occurred in all groups, but there was less femur neck bone loss by 1 year with calcitriol. As in other studies, the benefit of calcitriol waned after its discontinuation.

As might be anticipated with this activated form of vitamin D, hypercalcemia and hypercalciuria were common, seen in 18% and 59% of patients treated with calcitriol. Routine monitoring of urine and serum calcium is indicated if calcitriol is prescribed.

Calcitriol may have significant nonosteogenic benefits, which include recognized immunomodulatory and steroid-sparing actions. In a Turkish study of renal transplant recipients, patients who received calcitriol had lower PTH levels in the third year posttransplantation, as well as decreased requirements for pulse steroid doses. The increase in creatinine levels was also less in the calcitriol group. The authors concluded that calcitriol may reduce the rate of loss of renal function after renal transplant and protect renal allograft function. [103]

Vitamin D and calcium alone are clearly insufficient to prevent transplant-related bone loss. [104] Bisphosphonates are the drugs of choice for steroid-induced osteoporosis. [89] Although the sun is the major natural source of vitamin D, unnecessary exposure to ultraviolet light cannot be recommended because of the increased incidence of skin cancers in transplant recipients.


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