title: Differential effects of high prothrombin levels on thrombin generation depending on the cause of the hyperprothrombinemia.
abstract: BACKGROUND
  Hyperprothrombinemia, resulting from the prothrombin G20210A mutation or other causes, is associated with activated protein C (APC) resistance and increased thrombosis risk. When high prothrombin levels are a result of increased hepatic biosynthesis, these effects may be counteracted by concomitantly increased levels of the anticoagulant factors (particularly protein S). Differently, in prothrombin G20210A carriers only prothrombin levels are elevated.
  
  
  OBJECTIVE
  To investigate whether prothrombin G20210A carriers have a more severe hypercoagulable state than non-carriers with comparable prothrombin levels.
  
  
  METHODS
  Coagulation factor levels, thrombin generation (Calibrated Automated Thrombogram in the presence and absence of APC) and APC resistance were measured in normal (n = 132), heterozygous (n = 167) and homozygous (n = 3) individuals.
  
  
  RESULTS
  Prothrombin levels, thrombin generation and APC resistance were higher in carriers of the prothrombin G20210A mutation (especially those who had experienced venous thrombosis) than in non-carriers, whereas protein S and antithrombin levels were similar among genotype groups. Because individuals with high prothrombin levels in the absence of the prothrombin G20210A mutation tend to have all liver-synthesized factors elevated, carriers of the mutation had lower protein S and antithrombin levels than non-carriers with equally high prothrombin levels. Accordingly, they also generated more thrombin and showed a tendency toward higher APC resistance. Analogous effects, but less pronounced, were observed in homozygotes for the prothrombin A19911G polymorphism, which also upregulates prothrombin levels.
  
  
  CONCLUSIONS
  Individuals with hyperprothrombinemia as a result of prothrombin gene mutations generate more thrombin and tend to be more APC-resistant than individuals with comparable prothrombin levels because of other causes.
authors.affiliation: Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, the Netherlands. e.castoldi@bioch.unimaas.nl
authors.forename: E
authors.initials: E
authors.lastname: Castoldi
authors.forename: P
authors.initials: P
authors.lastname: Simioni
authors.forename: D
authors.initials: D
authors.lastname: Tormene
authors.forename: M C L G D
authors.initials: MC
authors.lastname: Thomassen
authors.forename: L
authors.initials: L
authors.lastname: Spiezia
authors.forename: S
authors.initials: S
authors.lastname: Gavasso
authors.forename: J
authors.initials: J
authors.lastname: Rosing
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D017931:DNA Primers; D005260:Female; D006580:Genetic Carrier Screening; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D011516:Prothrombin / Q000235:genetics / Q000378:metabolism*; D013917:Thrombin / Q000096:biosynthesis*
chemical_list: D017931:DNA Primers; D011516:Prothrombin; D013917:Thrombin