Parameters of the thrombogram are associated with serum 25-hydroxyvitamin D levels at baseline, but not affected during supplementation with vitamin D

Abstract Introduction In vitro studies indicate an anticoagulant effect of 1,25-dihydroxyvitamin D, and sun exposure may lower the risk of thrombotic events. Accordingly, an effect on haemostatic parameters could be expected after supplementation with vitamin D. Materials and Methods 158 obese or overweight subjects were included in a one year intervention study with supplementation with 40.000 IU vitamin D3 per week or placebo. All subjects were given 500 mg calcium daily. Plasminogen activator inhibitor 1 (PAI-1), tissue plasminogen activator antigen (tPA Ag), and tissue factor-induced thrombin generation over time in plasma assessed by the calibrated automated thrombogram (CAT) method as a parameter of over all thrombotic activity, were measured before and at the end of the study. Results Mean baseline serum 25(OH)D level was 61.8 nmol/L and increased in the vitamin D group to 145.6 nmol/L at the end of the study. At baseline there was a significant decrease in the CAT variables lag time and time to peak of the thrombogram across increasing serum 25(OH)D quartiles, whereas no significant associations between serum 25(OH)D and PAI-1 or tPA Ag were found. After one year, no significant differences were found between the vitamin D and placebo groups regarding change in any of the haemostatic parameters. Conclusions The association between lag time and time to peak in the CAT assay and serum 25(OH)D levels could indicate a pro-thrombotic state in subjects with high serum 25(OH)D levels, whereas the lack of effect of high dose vitamin D supplementation questions the causality of this relation.