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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Ruminant Diseases and Immunology Research » Research » Publications at this Location » Publication #203489
Title: The assessment of circulating 25(OH)D and 1,25(OH)(2)D: Where we are and where we are going

Author
item HOLLIS, BRUCE - UNIV SOUTH CAROLINA
item Horst, Ronald

Submitted to: The Journal of Steroid Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2006
Publication Date: 3/20/2007
Citation: Hollis, B.W., Horst, R.L. 2007. The assessment of circulating 25(OH)D and 1,25(OH)(2)D: Where we are and where we are going. Journal of Steroid Biochemistry and Molecular Biology. 103(3-5):473-476.

Interpretive Summary: Historically we have been taught that the main role of vitamin D in a healthy diet was to allow our bodies to build strong healthy bones and teeth. More recently scientist have discovered that vitamin D may have a broader role in helping the body fight infections and in preventing some form of cancer. These newly defined roles have lead to an explosion of interest in evaluating methods for monitoring the body’s vitamin D status. In order to become active vitamin D must go through a two-step activation process. The first step takes place in the liver to form 25-hydroxyvitamin D and the second step in the kidney to form 1,25-dihydroxyvitamin D. The liver form of vitamin D (25-hydroxyvitamin D) is the most abundant form of vitamin D that circulates in the blood. There is now generally agreement between scientist and clinicians that measuring the 25-hydroxyvitamin D form in the blood is the best indicator of vitamin D status. This report will review the current methods available for measuring vitamin D status and discussing the pros and cons of the different methodologies.

Technical Abstract: The field of vitamin D assay technology has progressed significantly over the past four decades. Further, the clinical utility of these measurements have moved from esoteric into mainstream clinical diagnosis. This movement has been fueled by the realization that vitamin D is involved in bodily systems beyond skeletal integrity. The clinical assay techniques for circulating 25(OH)D and 1,25(OH)2D have progressed away from competitive-protein binding assay (CPBAs) that utilize tritium reporters to radioimmunoassay (RIAs) that utilize both I**125 and chemiluminescent reporters. These advances have allowed direct serum analysis of 25(OH)D in an automated format that provides a huge sample throughput. Detection of circulating 25(OH)D can also be achieved utilizing direct high performance liquid chromatographic (hplc) or liquid chromatography coupled with mass spectrometry (LC-MS) techniques. These methods are accurate, however, they require expensive equipment and restrict sample throughput in the large clinical laboratory. Direct serum detection of 1,25(OH)2D is unlikely to occur for many reasons as a sample pre-purification will always be required. However, a semi-automated chemiluminescent detection system with automated sample preparation is in final development for the determination of circulating 1,25(OH)2D. These advances will allow both 25(OH)D and 1,25(OH)2D to be detected in an accurate, rapid fashion to meet the clinical demands we see emerging.