Associations of Cholecalciferol Supplementation with Thrombin Generation and Fibrin Clot Structure in Severe Vitamin D Deficiency: A Prospective Cohort Study

Introduction: Vitamin D deficiency has been associated with increased risks of both arterial and venous cardiovascular events. The underlying possible mechanisms remain incompletely understood, and whether vitamin D supplementation influences hemostasis has not been thoroughly assessed. We hypothesized that supplementation with vitamin D in deficient patients would lead to a less prothrombotic hemostatic profile, as measured by global coagulation assays and fibrin clot structure.

Methods: We enrolled adult patients attending the outpatient clinic of the Primary Care division of the University Hospitals of Geneva with a vitamin D deficiency (25-hydroxyvitamin-D3 (25-OHD)<25nmol/L) from 9.2016 to 5.2017, in whom a standard supplementation (oral cholecalciferol 300,000IU once, followed by 800IU per day) was prescribed. Exclusion criteria included ongoing cholecalciferol supplementation or anticoagulant treatment, renal insufficiency (GFR<30ml/min), BMI>30kg/m², cancer, and a recent hospitalization or infection. Blood was taken before supplementation and after 1-3 months. We evaluated standard coagulation times, thrombin generation assay, fibrin polymerization and clot lysis times (in triplicates). Paired t-tests with a two-sided alpha of 0.05 compared absolute mean differences of these measurements, and in secondary analyses relative differences of their geometric means.

Results: Among 48 mostly white and healthy adults (56% women), mean age and BMI were 43.8 years and 24.2kg/m². Prevalences of hypertension, smoking, diabetes and past cardiovascular disease were 23%, 29%, 13% and 2%, respectively. At a mean of 6.4 weeks after supplementation with cholecalciferol , 25-OHD levels increased in all participants, from an average of 17.9±4.6 (SD) nmol/L to 61.2±20.7 nmol/L. There were no change in aPTT, TP% and fibrinogen levels. Thrombin generation ETP decreased from 1384±218 to 1289±197 nM*min (absolute decrease of 95 nM*min, relative decrease of geometric means of 6.8%, p<0.0001). Thrombin peak values decreased (p<0.001), and time to peak and lag time increased (p<0.03). The maximum polymerization (absorbance) decreased from 0.43 to 0.40 OD (absolute decrease of 0.04, relative decrease of geometric means of 8.5%, p=0.001). Clot lysis time remained unchanged after supplementation.

Conclusions: Among non-obese patients with a severe vitamin D deficiency, a high-dose supplementation with cholecalciferol is associated with a reduction in thrombin generation and maximum fibrin polymerization. These findings suggest that vitamin D deficiency may be responsible for a potentially reversible prothrombotic profile.