Adult patients with Dexa scan (bone scan) z-scores < -1.0 (meaning low bone density) in at least one site will be selected for randomization. All patients who qualify for randomization will undergo baseline bloodwork for serum bone specific alkaline phosphatase (BSAP) and n-terminal telopeptides of collagen (NTX) levels. Recent bloodwork obtained as part of their ongoing long-term Pediatric Oncology and/or Endocrine clinic follow-up evaluation will be reviewed to exclude any baseline correctable confounding causes of osteopenia (low bone density). All women of childbearing potential will have a pregnancy test.