Serum Vitamin D, Platelet Function, and Bleeding in Primary ITP – Platelets Journal
Platelets Journal shared a post on LinkedIn about a recent article by Justin P. Oosterlee et al., adding:
“Recently published in Platelets!
“Effects of serum vitamin D on platelet function and bleeding in primary immune thrombocytopenia” by Justin P. Oosterlee, et al. (2026).
Bleeding in primary immune thrombocytopenia (ITP) is frequently milder than the platelet count would predict, and the disease also carries an elevated thrombotic risk.
Vitamin D deficiency (VDD) is common in ITP and has separately been linked to heightened platelet reactivity in healthy donors and in patients receiving dual antiplatelet therapy, making altered platelet function a plausible connecting mechanism.
Oosterlee and colleagues tested this in 79 adults from the Vienna ITP Biobank, of whom 13 had severe VDD, 52 had VDD and 14 were vitamin D sufficient.
Across PAC-1 binding to activated GPIIb/IIIa and P-selectin expression, measured naïve and after stimulation with TRAP-6, ADP, arachidonic acid and CRP-XL, alongside soluble P-selectin, mean platelet volume and SMOG bleeding scores, no parameter differed convincingly by vitamin D status.
Soluble P-selectin was highest in the VDD group, but the evidence was weak (p = .057) and did not follow the direction expected of a dose effect.
Adjustment did not alter the picture: ordinal logistic regression accounting for platelet count found no relationship with bleeding severity (Χ² = 5.65, p = .342), and multivariable models using splines to permit non-linear effects found none with any functional readout.
Platelet count itself carried the signal, a doubling associated with 42.7% and 32.5% greater GPIIb/IIIa and P-selectin expression following TRAP-6 (both p less than .001). Sex produced the one clear difference, with women scoring higher for bleeding than men (median SMOG 4 vs 0; p = .009).
Sensitivity analyses adjusting for steroid and TPO-RA use, and excluding supplemented patients, left the findings intact.”
Title: Effects of serum vitamin D on platelet function and bleeding in primary immune thrombocytopenia
Authors: Justin P. Oosterlee, Dino Mehic, Tim Dreier, Alexander Tolios, Beate Eichelberger, Helmuth Haslacher, Cihan Ay, Ingrid Pabinger, Johanna Gebhart

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