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Should Vitamin D Be Prescribed with Tenofovir/FTC?
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Reported by Jules Levin
ICAAC/IDSA Oct 28 2008 Wash DC
K. CHILDS, S. FISHMAN, K. BATEMAN, S. FACTOR, C. WYATT, M. MULLEN, A. BRANCH; Mount Sinai School of Medicine, New York, NY.
AUTHOR CONCLUSION
Thirty-nine percent of subjects exposed to the combination of TDF/FTC and suboptimal 25(OH)D had elevated PTH
Patients on TDF/FTC should have 25(OH)D and PTH levels checked
Low 25(OH)D and TDF/FTC appear to act synergistically to increase PTH level
We hypothesize that TDF/FTC causes a reduction in whole body calcium, which
results in elevated PTH (model)
Research is needed to investigate whether prophylactic use of vitamin D3
supplements and calcium citrate will prevent increases in PTH and preserve bone.
BACKGROUND
Abnormalities of bone and calcium are common in HIV patients.1
Tenofovir (TDF) decreases bone density in children and adults and causes skeletal lesions in fetal primates.2,3
Vitamin D insufficiency is common in the population4
Low vitamin D [measured by 25(OH)D] is a known cause of secondary hyperparathyroidism
Secondary hyperparathyroidism indicates abnormal calcium metabolism and causes osteopenia and osteoporosis.
In subjects with normal renal function, high PTH is also associated with LV hypertrophy, incident hypertension, higher risk of metabolic syndrome and poorer performance on cognitive tests5,6
We aimed to assess vitamin D status and to determine its influence on the relationship between anti-retroviral medications and abnormal calcium/bone metabolism.
We hypothesized that the effect of TDF on bone is mediated via effects on the 25(OH)D-calcium-PTH axis
METHODS
An IRB approved cross-sectional study with medical record review and interviews was done on 51 HIV-infected men taking anti-retroviral therapy (ART) with normal serum calcium.
Blood 25(OH)D and PTH levels were assayed.
TDF was always used with FTC.
RESULTS
25(OH)D insufficiency was common
Among subjects on ART who had low vitamin D:
PTH was above the ULN in 39% of those on tenofovir/emtricitabine
(TDF/FTC) versus 7% on TDF-sparing regimens (p= 0.036)
Median plasma PTH was 80 pg/ml on TDF/FTC versus 55 pg/ml on ART without TDF/FTC (p=0.02).
No subject with optimal 25(OH)D levels had elevated PTH
Multivariable analysis showed that 25(OH)D levels (p=0.03) and TDF/FTC use (p=0.04) were independently associated with plasma PTH, serum creatinine was not.
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