Selecting a preferred marker of vitamin D levels: 25(OH)D and/or 1,25(OH)2D?

At present, there is no consensus in the medical community on the nature and extent of the effects of 25(OH)D and 1,25(OH)2D on such important biochemical parameters as serum concentrations of parathyroid hormone and calcium, on changes in serum concentrations of calcidiol and calcitriol associated with human aging, and on the nature of the relationship between 25(OH)D and 1,25(OH)2D. At the same time, on the basis of a large-scale database of the European, practically healthy population of white ethnicity, we conducted statistical studies aimed at choosing the most representative marker of vitamin D levels, as well as clarifying the nature of the interaction between 25(OH)D and 1,25(OH)2D. Correlation analysis data of 60,680 practical healthy, non-pregnant and Caucasian residents of European countries allowed us to draw the following conclusions: increase 25(OH)D and 1.25 (OH) 2D are accompanied by a proportional increase in serum calcium and a proportional decrease in serum parathyroid hormone; as a person ages, the levels of 25(OH)D and 1.25 (OH) 2D decrease; serum concentration of 1,25(OH)2D is always statistically more stable with serum calcium and parathyroid hormone concentrations, as well as with age, compared to 25(OH)D; 25(OH)D and 1,25(OH)2D are related to each other by an extremely stable (p=10-9) directly proportional relationship. It seems to us that for the practically healthy European population, when it comes only to improving well-being and quality of life, the measurement of the total level of 25(OH)D in winter and spring is quite sufficient. In the presence of any serious medical condition, especially those associated with impaired vitamin D metabolism, it seems more productive to measure not only 25(OH)D, but also 1,25(OH)2D.