Vitamin D Regimen May Treat SHPT in Renal Transplant Patients
Mariana S. Markell, MD
PHILADELPHIA—Cholecalciferol with or without doxercalciferol may be an appropriate treatment for secondary hyperparathyroidism (SHPT) in kidney transplant recipients, according to the findings of a small study presented at Kidney Week 2011.
The study showed that vitamin repletion can be accomplished in six weeks with an accompanying decrease in PTH levels of about 30%. Mariana S. Markell, MD, and Sima Terebelo, RPA-C, MPH, of the State University of New York Downstate Medical Center in Brooklyn enrolled 39 stable renal transplant recipients with HPTH and hypovitaminosis D. They randomized patients to receive cholecalciferol 1,000 U daily plus placebo or cholecalciferol 1,000 U plus 0.5 mcg doxercalciferol daily for six months. Investigators measured parathyroid hormone (PTH) levels at four weeks. Doxercalciferol (or placebo) dose was titrated up by 0.5 mcg if PTH values had not decreased.
Thirty-three patients completed the study. Three from each group had dropped out. No patient dropped out because of hypercalcemia. The investigators observed no difference in response to cholecalciferol or doxercalciferol with respect to PTH so they combined the groups for evaluation of treatment effect.
PTH levels decreased significantly from 189.7 pg/mL at baseline to 134.7 pg/mL by 6 months. Levels of 25-hydroxyvitamin D increased significantly from 16.4 to 30.8 ng/mL, but levels of 1,25-dihydroxyvitamin D and fibroblast growth factor-23 did not change significantly (53.5 vs. 56.1 ng/mL and 97.9 vs. 109.9 pg/ml.
Previous studies looking at vitamin D replacement in kidney transplant recipients have used supra-pharmacologic doses (100,000 U cholecalciferol), which put patients at risk for hypercalcemia and possible immunologic effects. Dr. Markell's team was able to replace vitamin D in patients with 1000 U over six months, with a very low rate of side effects.
“Replacement of vitamin D resulted in a significant fall in PTH levels, and we recommend this approach prior to treating with cinacalcet in transplant patients who are normocalcemic with hypovitaminosis D,” said Dr. Markell, who is Associate Professor of Medicine.
She noted that she and her colleagues studied only patients with good kidney function and who were at least one year post-transplant, so “the results may not be translatable to patients immediately post-transplant, or with poor kidney function, and these populations should be studied.”
“As vitamin D deficiency has been implicated in cardiovascular as well as other disease risk, long-term replacement studies should be performed in patients with kidney transplants, the majority of whom are vitamin D deficient following years of CKD,” she said.