Elevated serum thrombopoietin and interleukin-6 concentrations in thrombocytosis associated with inflammatory bowel disease

Reactive thrombocytosis is a typical feature in inflammatory bowel disease (IBD), The question arose as to whether the normal negative feedback regula tion of the concentration of thrombopoietin (TPO) in blood was altered in I BD patients. We measured serum immunoreactive TPO in 30 patients with activ e IBD, 29 patients with inactive IBD, and 56 healthy controls, The results were related to platelet and leukocyte counts and to the serum concentratio n of interleukin 6 (IL-6). Patients with active IBD exhibited significantly increased TPO levels (medians 112 pg/ml vs. 90 pg/ml in controls, p < 0.05 ) in association with thrombocytosis (428 platelets/nl blood vs. 241 platel ets/nl blood in controls), leukocytosis, and increased IL-6 levels (12.9 pg /ml vs. 2.5 pg/nl in controls). In patients with inactive IBD, only platele ts (322/nl) and leukocytes were above normal. Although the observation of i ncreased TPO and IL-6 levels provides an explanation for the occurrence of thrombocytosis in IBD, the pathogenetic mechanisms underlying the elevated TPO level still need to be identified.