Measurement of the Free Fraction of 25-hydroxyvitamin D in Serum

September 18, 2015 updated by: University of Tromso
In the circulation 25-hydroxyvitaminD (25(OH)D) is bound to the vitamin D binding protein (DBP) and albumin. According to the free hormone hypothesis, it is, however, the free fraction that is biologically active. Polymorphisms in DBP are related to the serum level of 25(OH)D. As these polymorphisms may also affect the binding affinities for 25(OH)D, the total serum 25(OH)D may not necessary reflect the free fraction. To test this hypothesis, we will calculate the free fraction of 25(OH)D by correction for DBP and albumin content, and also measure free 25(OH)D from equilibrium dialysis and ultra filtration. Furthermore, we will relate total serum 25(OH)D as well as the free and biologically active (free- albumin-bound) 25(OH)D to the well established vitamin D effect marker serum parathyroid hormone as well as to the RNA expression in peripheral blood to evaluate the biological importance of the free versus the total fraction of 25(OH)D. We will invite 300 subjects from an ongoing vitamin D supplementation study to participate in the study which will be one visit only and include collection of blood samples.

Study Overview

Status

Completed

Conditions

Study Type

Observational

Enrollment (Actual)

78

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Norway
      • Tromsø, Norway, 9037
        • University of Tromsø

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

25 years to 85 years (ADULT, OLDER_ADULT)

Accepts Healthy Volunteers

Yes

Genders Eligible for Study

All

Sampling Method

Non-Probability Sample

Study Population

Subjects with known impaired glucose tolerance

Description

Inclusion Criteria:

  • Impaired glucose tolerance
  • living in the Tromsø area

Exclusion Criteria

  • pregnancy
  • serious illness

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Subjects with impaired glucose tolerance

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Free fraction of 25(OH)D
Time Frame: 1 day
1 day

Secondary Outcome Measures

Outcome Measure
Time Frame
DBP polymorphisms
Time Frame: 1 day
1 day

Other Outcome Measures

Outcome Measure
Time Frame
RNA expression in peripheral blood
Time Frame: 1 day
1 day

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Tromso

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start

February 1, 2013

Primary Completion (ACTUAL)

June 1, 2015

Study Completion (ACTUAL)

August 1, 2015

Study Registration Dates

First Submitted

January 10, 2013

First Submitted That Met QC Criteria

January 15, 2013

First Posted (ESTIMATE)

January 18, 2013

Study Record Updates

Last Update Posted (ESTIMATE)

September 22, 2015

Last Update Submitted That Met QC Criteria

September 18, 2015

Last Verified

September 1, 2015

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • Tromsø-Endo-2013-1

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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