Vitamin D was named in 1921 as the fourth vitamin to be discovered, identified as a factor in cod liver oil which cured rickets and was distinct from vitamin A. The relationship between ultraviolet light exposure and the production of vitamin D was quickly recognised, and the structure of various vitamin D metabolites was identified in the 1930's.
More than 90 years have elapsed since the discovery of vitamin D, and during much of this period it was thought that its biological role was limited to calcium metabolism and preventing bone disease and fully understood. During the last decade, however, there has been increasing recognition of the broader role of vitamin D metabolites in human biology beyond bone. Concern about inadequate vitamin D status in a substantial proportion of the population and particularly those living at higher Northern or Southern latitudes. This has resulted in an explosion of renewed scientific interest in vitamin D, taken up by the popular press and of increasing concern to Governments and individual members of the public alike. One of the consequences of this has been a proliferation of guidelines and recommendations around vitamin D intake, the use of supplements and exposure to sunlight. In turn, many clinical laboratories have seen (and continue to see) a dramatic increase in requests for measurement of biomarkers related to vitamin D status.
Against this background, it was particularly appropriate that the 13th Bergmeyer Conference, held from 5 - 7 March 2012 focused on the topic of Vitamin D. This issue of the Journal contains papers based on the presentations which were given at the Conference.
The participants in this conference came from a wide range of professional backgrounds, including research scientists, hospital scientists, clinical laboratory scientists and clinicians. The faculty brought consisted of many of the world's leading researchers on Vitamin D who gave state of the art presentations on a wide range of aspects of vitamin D biology, including measurement and standardization. All of the speakers at the conference have provided papers for this issue of the journal, and we are grateful for their contributions. Together, this provides a comprehensive overview of vitamin D as we understand it in 2012.
The Bergmeyer Conference is named after and dedicated to Professor Hans-Ulrich Bergmeyer to honour his outstanding achievements in biochemistry and the area of standardization. The conference is financially sponsored by Roche Diagnostics in the form of an unrestricted educational grant, and the topic is chosen and the programme put together by the Scientific Division of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC).
As for all of the previous Conferences, Anders Kallner again took over the main responsibility of editing these proceedings. Janet Smith summarised discussions and put them in their proper context. Paola Bramati at the IFCC office supported the organization of the scientific aspects of the Conference. Last but not least, Joe Passarelli and his staff at Roche Diagnostics carried the burden of organizing the Conference in Eibsee, Germany, and in enabling us to achieve, once again, an outstanding meeting. We are grateful to them all.
A note on terminology
In this supplement the following terminology is used.
Vitamin D refers to cholecalciferol or ergocalciferol, or both.
Vitamin D3 refers to cholecalciferol, Vitamin D2 to ergocalciferol.
25-hydroxy-cholecalciferol is abbreviated 25(OH)D3, 25-hydroxy-ergocalciferol 25(OH)D2.
1,25-dihydroxycholecalciferol and 24,25-dihydroxycholecalciferol are written 1,25(OH)2D3 and 24,25(OH)2D3, respectively.
The notation 25(OH)D concentration is frequently used and refers to the sum of the concentrations of 25(OH)D3, and 25(OH)D2.
In some of the articles the concentration of 25(OH)D is abbreviated according to the IFCC/IUPAC rules as S-25(OH)D. This is then explained in a footnote.
In all other measurements the name of the compound is given as above.
The concentration of 25(OH)D is expressed in the molar unit: nmol/L Although not fully comparable (Tienpoint et al. this issue) a conversion factor of 2.46 is often used; thus, 1 μg/L (1 ng/mL) equals 2.46 nmol/L. This relation is acceptable for most practical purposes.
It has become important in this series of publications to explicitly state what is measured since it is not always clear what is otherwise meant.
Intakes are given as amounts, preferably in mass units i.e. μg, but may also be expressed in activity units IU although this is discouraged. 40 IU = 1 μg.
Calcidiol (Calcifediol) is synonymous with 25(OH)D3 but its use deprecated.
Calcitriol is synonymous to 1,25(OH)2D3 but its use deprecated.
Alfacalcidol is 1α(OH)D3 which is hydroxylated to 1,25(OH)2D3 in vivo.
VDR The 1,25(OH)2D3 receptor or Vitamin D receptor
Table I. Years and topics of the Bergmeyer Conferences.