The purpose of this study is to test the effects of Vitamin D on renal phosphate and bone loss, which are common in HIV infected adolescents and young adults being treated with tenofovir.

ATN 063 tests the hypothesis that in a population of adolescents and young adults with HIV infection who are being treated with tenofovir as part of an antiretroviral (ARV) combination regimen, vitamin D supplementation will decrease renal phosphate loss, increase plasma phosphate, decrease plasma PTH, and improve markers of bone turnover, including a decrease in plasma N-telopeptide and BAP.

Inclusion Criteria:

• Age 18 years and 0 days through 24 years and 364 days
• HIV-1 infection as documented by any licensed ELISA test kit and confirmed by Western blot, HIV-1 culture, HIV-1 antigen, plasma HIV-1 RNA, or a second antibody test by a method other than ELISA at any time prior to study entry
• Currently being treated with a stable FDA-approved ARV combination therapy, containing > 3 antiretrovirals, for > 28 days, according to HRSA guidelines. Treatment regimen will not be started or changed for the purposes of participation in this study. Subjects will be receiving therapy at the direction of their treating physician
• Willingness to remain on the same ARV combination therapy for the 12-week duration of the study
• Ability and willingness to participate in the study by providing written informed consent
• Willingness to be randomized to receive either vitamin D or placebo

Exclusion Criteria:

• Prior hypersensitivity to vitamin D
• History of arteriosclerosis, renal stones, glomerulonephritis, nephrotic syndrome, or hypercalcemia
• Lactation or current pregnancy
• Active therapy for malignancy
• Known presence of gastrointestinal disease that would interfere with drug administration or absorption
• Serological evidence of Hepatitis B surface antigen (HBsAg)
• Confirmed creatinine clearance < 90 ml/min (calculated GFR from serum creatinine using the MDRD formula)
• Grade 3 or higher clinical toxicity