Tumor Necrosis Factor Decreases Vitamin D Dependant Calcium Absorption

This study is a pilot study to determine whether patients with TNFα excess have decreased calcium absorption in response to calcitriol (1,25-dihydroxyvitamin D, the active form of vitamin D) compared to normal controls. This initial pilot study is being done to determine if it is feasible to conduct a study where TNFα could be blocked (e.g., by anti-TNFα therapy such as Enbrel® or Remicade®) to improve vitamin D dependant calcium absorption and thus bone health.