Polymorphisms in the Vitamin D System and Health

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT01395303
Recruitment Status : Completed
First Posted : July 15, 2011
Last Update Posted : November 11, 2016
Information provided by (Responsible Party):
Rolf Jorde, University of Tromso

Brief Summary:
Polymorphisms in the vitamin D system appear to affect the serum 25(OH)D levels. If so one would expect these polymorphisms to be associated with vitamin D related conditions and diseases, which will be tested in the present study including DNA analyses in 9700 subjects

Condition or disease
Infarction Stroke Diabetes Fracture Aortic Stenosis Cancer Death

Detailed Description:

Vitamin D, which is essential in calcium metabolism, is produced in the skin after sun exposure or obtained from food, mainly fatty fish or vitamin D supplements. For activation vitamin D must be hydroxylated in the liver to 25(OH)D and thereafter in the kidney to 1,25(OH)2D. In the circulation 25(OH)D and 1,25(OH)2D are bound to a carrier protein (DBP), and for 1,25(OH)2D to exert its effect it has to bind to the vitamin D receptor (VDR).

The serum level of 25(OH)D, which is the metabolite used to evaluate a person's vitamin D status, is in part genetically determined and several polymorphisms with effects on serum 25(OH)D have been identified. These polymorphisms, where the minor allele frequencies vary between 16 and 40 %, appear as important for the serum 25(OH)D level as the effect of season, physical activity or vitamin D supplementation.

Vitamin D is not only vital for the skeleton, but appears to be related to a number of health outcomes, including mortality as previously demonstrated in the Tromsø study. However, as the serum level of 25(OH)D is strongly influenced by life-style factors that are also related to health outcomes, it is difficult to decide whether the relation between vitamin D and health is causal or not.

On the other hand, the polymorphisms are not influenced by life-style, and the effect of the polymorphisms will be life-long. Accordingly, they may be a better marker of vitamin D status than a single serum 25(OH)D measurement. Furthermore, there are a number of polymorphisms regarding the vitamin D receptor (VDR) that may be associated with health.

In the present study we will therefore relate the polymorphisms affecting the serum 25(OH)D level and the function of the VDR, with anthropometric and biochemical measures, mortality, diseases and risk factors for disease. DNA will be obtained from the 4th Tromsø study.

If we find the expected associations between the polymorphisms and diseases, this will further strengthen the role of vitamin D in human health, and may be important for recommendations regarding vitamin D supplementation. Considering the high prevalence of vitamin D deficiency world wide, this may potentially have huge consequences for public health.

The main purpose of the present study is the vitamin D system, but in the Tromsø study we have previously also found a number of associations between thyroid and androgen function and health. Obtaining DNA for analysis will be the major cost in the project, whereas analyses of individual polymorphisms are relatively cheap. We will therefore also include polymorphisms regarding thyroid and androgen function.

Study Type : Observational
Actual Enrollment : 9700 participants
Time Perspective: Retrospective
Official Title: Polymorphisms in the Vitamin D System and Health
Study Start Date : April 2011
Actual Primary Completion Date : July 2016
Actual Study Completion Date : August 2016

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Vitamin D
Drug Information available for: Vitamin D

myocardial infarction
subjects with myocardial infarction in the Tromsø study end point registry
type 2 diabetes
subjects with type 2 diabetes in the Tromsø study end point registry
subjects with stroke in the Tromsø study end point registry
subjects with fracture in the Tromsø study end point registry
subjects with cancer in the Tromsø study end point registry
subjects registered as dead in the Tromsø study end point registry
aortic stenosis
subjects with aortic stenosis in the Tromsø study end point registry
control group
randomly selected controls from the Tromsø study

Biospecimen Retention:   Samples With DNA
DNA from blood clots

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Ages Eligible for Study:   30 Years to 90 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Sampling Method:   Probability Sample
Study Population
Subjects from the fourth Tromsø study performed in 1994-1995 who had blood samples taken for later DNA analyses

Inclusion Criteria:

  • participated in the fourth Tromsø study, later registered in our end point registry or selected as a control subject

Exclusion Criteria:

  • lacking DNA sample

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT01395303

University of Tromsø
Tromsø, Norway, 9037
Sponsors and Collaborators
University of Tromso
Principal Investigator: Rolf Jorde, Professor University of Tromso

Publications automatically indexed to this study by Identifier (NCT Number):
Responsible Party: Rolf Jorde, Professor, University of Tromso Identifier: NCT01395303     History of Changes
Other Study ID Numbers: UIT-ENDO-2011-2
First Posted: July 15, 2011    Key Record Dates
Last Update Posted: November 11, 2016
Last Verified: November 2016

Keywords provided by Rolf Jorde, University of Tromso:
aortic stenosis
vitamin D
thyroid hormones

Additional relevant MeSH terms:
Aortic Valve Stenosis
Pathologic Processes
Heart Valve Diseases
Heart Diseases
Cardiovascular Diseases
Ventricular Outflow Obstruction
Vitamin D
Growth Substances
Physiological Effects of Drugs
Bone Density Conservation Agents