Clinical Trial: Does Treatment of Hypovitaminosis D Increase Calcium Absorption?

Study Status: Completed
Recruit Status: Completed
Study Type: Interventional

Official Title: Does Treatment of Hypovitaminosis D Increase Calcium Absorption?

Brief 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 Summary:

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
Sponsor: University of Wisconsin, Madison

Current Primary Outcome: Change in Intestinal Calcium Absorption From Baseline to One Month [ Time Frame: 1 month ]

percent and true fractional calcium absorption


Original Primary Outcome: The primary outcome of this study is the change in intestinal calcium absorption from baseline to vitamin D repletion, by paired t-test. [ Time Frame: 1 month ]

Current Secondary Outcome:

Original Secondary Outcome:

  • The effect of vitamin D therapy upon calcium retention within bone as measured one year change in whole body, lumbar spine and hip bone mass [ Time Frame: 1 year ]
  • The relationship between severity of initial hypovitaminosis D and the increment in intestinal calcium absorption [ Time Frame: 1 month ]
  • The effect of vitamin D repletion upon physical function, quality of life and muscle mass. [ Time Frame: 1 year ]
  • To compare the clinical benefits of vitamin D repletion among women with and without secondary hyperparathyroidism. [ Time Frame: 1 month ]


Information By: University of Wisconsin, Madison

Dates:
Date Received: December 19, 2007
Date Started: January 2005
Date Completion:
Last Updated: September 13, 2012
Last Verified: September 2012