Does Treatment of Hypovitaminosis D Increase Calcium Absorption?
Condition: Osteoporosis; Osteopenia; Vitamin D Deficiency; Hypoparathyroidism; Hypercalciuria; Hypercalcemia
MeSH terms: Osteoporosis; Bone Diseases, Metabolic; Rickets; Vitamin D Deficiency; Avitaminosis; Hypercalcemia; Hypoparathyroidism; Hypercalciuria
Study type: Interventional
Phase: Phase 4

Summary: 
      The purpose is to perform a one-year study designed to assess whether treatment of
      hypovitaminosis D increases intestinal absorption of calcium, subsequent retention of calcium
      within bone, decreases bone turnover, and favorably impacts upon skeletal muscle mass,
      functional status, measures of physical function and quality of life. I hypothesize that
      treatment of hypovitaminosis D results in improved intestinal calcium absorption, greater
      retention of calcium within the bone reservoir and improved physical function, quality of
      life and muscle mass.
    

Detailed description: 
      Postmenopausal women with vitamin D insufficiency will participate in this one-year study. We
      will study the change in intestinal calcium absorption from baseline (vitamin D
      insufficiency) to follow up (vitamin D repletion and whether increased absorption results in
      subsequent increased retention of calcium within bone over the one-year interval as measured
      by bone densitometry. We will also study the effect of vitamin D repletion upon whole body
      muscle mass, quality of life and physical function.

      A review of medical records and a screening visit will determine eligibility. Eligible and
      consenting subjects will present to the GCRC in the early morning and following baseline
      labs, will consume breakfast with a glass of orange juice enriched with a stable calcium
      isotope, and will receive 3 mg of another stable calcium isotope by intravenous injection.
      Over the next eight hours, blood will be taken a total of 9 more times and over the first 24
      hours, all urine and stool will be collected for measurement of its calcium content.

      Subsequently for the next five days, women will collect three urine specimens daily. Women
      will then receive vitamin D to treat vitamin D deficiency. Once vitamin D repletion is
      accomplished, all women will repeat their 24-hour visit and subsequent five-day urine
      collections. Women will maintain vitamin D repletion by taking a twice monthly tablet (50,000
      IU) of vitamin D2. To confirm vitamin D repletion and safety over the full one year study,
      additional study visits will occur at 3, 6 and 12 months.

      A bone density test at screening and twelve months will allow us to assess the effect of
      vitamin D repletion on whole body bone mass and skeletal mass. At each GCRC stay, 3, 6 and 12
      months, women will complete questionnaires regarding quality of life and functional status
      and will perform the Timed Up and Go Test. Because we wish to maintain and confirm constant
      calcium intake throughout the one- year study, women will complete a calcium questionnaire at
      baseline, 3, 6 and 12 months.

      With each subject's consent, we will collect one tube of blood and isolate its DNA. When
      sufficient knowledge is available regarding the pathophysiologic mechanisms whereby genetic
      polymorphisms impact calcium homeostasis, we will test for such DNA polymorphisms and relate
      genetic information with other data collected on calcium homeostasis.
    

Intervention name(s): Vitamin D
Intervention type(s): Drug
Intervention description(s): 50,000 IU po qd for 15 days and 50,000 IU po twice month for 10 months (until final study visit at one year)
Other intervention name(s): Vitamin D2; Ergocalciferol
Intervention MeSH terms: Vitamin D; Ergocalciferols; Cholecalciferol; Vitamins
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Calcium Absorption; Intestinal Absorption of Calcium; Fractional Calcium Absorption; Stable Calcium Isotopes; Hypovitaminosis D; Vitamin D; Bone Mineral Density; Physical Function