Plasma thrombopoietin levels in liver cirrhosis and kidney failure

Relationship between baseline clinical characteristics and efficacy of lusutrombopag in thrombocytopenic patients with chronic liver disease: post hoc analysis of two placebo-controlled phase 3 trials

OBJECTIVE

Lusutrombopag is a thrombopoietin receptor agonist approved to treat thrombocytopenia in patients with chronic liver disease (CLD). This post hoc analysis of the Japanese L-PLUS 1 and global L-PLUS 2 trials aimed to clarify factors related to platelet count increase after lusutrombopag treatment.

METHODS

In L-PLUS 1, Pearson's correlation coefficients were used to evaluate correlations between platelet count and spleen index, thrombopoietin concentration, white blood cell (WBC) counts, and red blood cell counts (intent-to-treat [ITT] population). Associations between platelet count increase after lusutrombopag treatment and each parameter were assessed by regression analysis and mixed-effect model for repeated measures (MMRM). Associations between time-dependent changes in platelet count increase and each parameter were also examined in the L-PLUS 2 lusutrombopag ITT population by MMRM.

RESULTS

In L-PLUS 1, the baseline platelet count was correlated with pretreatment spleen index (r = -0.23, 95% confidence interval [CI] -0.41 to -0.03) and WBC count (r = 0.26, 95% CI 0.06 to 0.43). No selected parameters were associated with the maximum platelet count increase from baseline. Patients with WBC counts below the normal range showed smaller platelet count increases after lusutrombopag treatment than patients with WBC counts within the normal range (p = .0028). In L-PLUS 2 (p = .0533), findings were similar and confirmed by larger pooled data of L-PLUS 1/L-PLUS 2 (p = .0021).

CONCLUSIONS

This post hoc analysis revealed a possible association between baseline WBC count and platelet count increase after lusutrombopag treatment. WBC count could be a relevant factor for lusutrombopag efficacy.

Thrombocytopenia: Perioperative Considerations for Patients Undergoing Cardiac Surgery

The etiologies of thrombocytopenia in patients presenting for cardiac surgery are extensive, but clinically relevant conditions generally can be categorized by those related to decreased platelet production or increased platelet destruction. Many causes require mere acknowledgment and availability of allogeneic platelet transfusion; others have unique considerations for which providers should be familiar. The purpose of this review is to provide an overview of the common causes of thrombocytopenia, summarize the literature, and discuss perioperative considerations for patients undergoing cardiac surgery.

The Kidney as an Endocrine Organ

The column in this issue is supplied by Vinay Acharya, D.O., and Juan Jose Olivero, M.D. Dr. Acharya is a nephrology fellow at Houston Methodist Hospital. He earned his Doctor of Osteopathic Medicine degree at Arizona College of Osteopathic Medicine and completed an internal medicine residency at Houston Methodist Hospital. Dr. Olivero is a nephrologist at Houston Methodist Hospital and a member of the hospital's Nephrology Training Program. He obtained his medical degree from the University of San Carlos School of Medicine in Guatemala and completed his residency and nephrology fellowship at Baylor College of Medicine in Houston, Texas.

Hypersplenism in liver disease and SLE revisited: current evidence supports an active rather than passive process

BACKGROUND

Active and passive theories have been advanced to explain splenomegaly and cytopenias in liver disease. Dameshek proposed active downregulation of hematopoiesis. Doan proposed passive trapping of blood components in a spleen enlarged by portal hypertension. Recent findings do not support a passive process.

DISCUSSION

Cytopenias and splenomegaly in both liver disease and systemic lupus erythematosus (SLE) poorly correlate with portal hypertension, and likely reflect an active process allocating stem cell resources in response to injury. Organ injury is repaired partly by bone-marrow-derived stem cells. Signaling would thus be needed to allocate resources between repair and routine marrow activities, hematologic and bone production. Granulocyte-colony stimulating factor (G-CSF) may play a central role: mobilizing stem cells, increasing spleen size and downregulating bone production. Serum G-CSF rises with liver injury, and is elevated in chronic liver disease and SLE. Signaling, not sequestration, likely accounts for splenomegaly and osteopenia in liver disease and SLE. The downregulation of a non-repair use of stem cells, bone production, suggests that repair efforts are prioritized. Other non-repair uses might be downregulated, namely hematologic production, as Dameshek proposed.

SUMMARY

Recognition that an active process may exist to allocate stem-cell resources would provide new approaches to diagnosis and treatment of cytopenias in liver disease, SLE and potentially other illnesses.

Association between circulating thrombopoietin levels and cardiovascular risk prediction scores in renal transplant recipients

BACKGROUND/AIMS

The 7-year Major Adverse Cardiovascular Events Calculator (CRCRTR-MACE) predicts cardiovascular events (CVE) in renal transplant recipients (RTR), and thrombopoietin (TPO) is a humoral inflammatory factor implicated in cardiovascular disease (CVD). The aim of the study was to determine if circulating TPO levels in stable RTR are positively associated with variable(s) in the CRCRTR-MACE score.

METHODS

CRCRTR-MACE scores were calculated in 95 stable RTR. TPO levels were measured by multiplexed fluorescent bead-based immunoassay in all patients and 48 controls. Multivariate analysis (MVA) was performed between TPO and CV risk variables and patient demographics. Stepwise regression with backward elimination of insignificant variables estimated the impact of risk variables on TPO levels. Significance was defined at p < 0.05. Normalized data were presented as mean ± SD and non-normalized data as median (maximum to minimum).

RESULTS

The risk of a CVE within 7 years as predicted by the median was 9.97% (range 1.93-84.2). The percentage of patients who were above 20% risk for a CVE was 28.4%. Control TPO level of 170.41 (4.4-995.9) pg/ml was significantly lower than that of 237.90 (32.77-1,386.79) pg/ml in RTR (p = 0.010). TPO level correlated significantly with the total CRCRTR-MACE score (R = 0.310, p = 0.004), smoking (p = 0.009) and eGFR (R = -0.275, p = 0.012) but not with age, diabetes, LDL level or history of CVE. Only the total CRCRTR-MACE score (p = 0.013) and smoking (p = 0.009) remained significant in the MVA. Stepwise regression estimated that smoking increased TPO levels by 206.28 pg/ml and each 10% increase in CRCRTR-MACE score increased TPO levels by an additional 44.4 pg/ml.

CONCLUSION

TPO levels are increased in RTR with high CRCRTR-MACE, particularly in smokers with diminished eGFR. Circulating TPO may serve as a biomarker and treatment target for CVD in RTR.

Rifaximin improves thrombocytopenia in patients with alcoholic cirrhosis in association with reduction of endotoxaemia

BACKGROUND

Thrombocytopenia is a major haematological disorder of cirrhosis with unclear pathogenesis. Endotoxaemia resulting from intestinal bacterial overgrowth could reduce platelet counts directly or through cytokine release.

AIMS

To correlate endotoxaemia with platelet counts and study the effects of intestinal decontamination with rifaximin on thrombocytopenia in relation to changes in endotoxin and cytokine concentrations in patients with alcoholic cirrhosis.

METHODS

Platelet counts, plasma endotoxin levels and serum interleukin-1 (IL-1), interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) levels were measured in 23 thrombocytopenic cirrhotic patients (platelet count<150 000/μl) before and after 4-week treatment with rifaximin 1200 mg/d (n = 13) or no treatment (n = 10) and at baseline in 10 cirrhotic patients without thrombocytopenia; spleen size was measured at baseline in all patients.

RESULTS

Endotoxin and IL-6 levels were significantly higher in patients with thrombocytopenia than in those without thrombocytopenia (2.76 ± 0.69 vs. 0.64 ± 0.09 EU/ml; P < 0.001 and 24.26 ± 3.38 vs. 2.66 ± 0.74 pg/ml; P = 0.001 respectively). Platelet counts were inversely correlated with endotoxin levels (r = -0.589; P = 0.003), Child-Pugh score (r = -0.625; P = 0.001), IL-6 levels (r = -0.464; P = 0.02) and spleen size (r = -0.455; P = 0.02) in patients with thrombocytopenia. Following rifaximin, platelet counts increased significantly (83 100 ± 9700 vs. 99 600 ± 11 200/μl; P = 0.006) in line with significant reductions in endotoxin (1.28 ± 0.41 vs. 2.54 ± 0.86 EU/ml; P = 0.005), IL-1 (3.1 ± 0.5 vs. 4.4 ± 1.2 pg/ml; P = 0.04), IL-6 (12.8 ± 2.5 vs. 21.1 ± 4.2 pg/ml; P = 0.01) and TNF-α (3.6 ± 1.3 vs. 5.8 ± 1.7; P = 0.02) levels. Platelet count changes were correlated with the changes in endotoxin (r = 0.573; P = 0.04), TNF-α (r = 0.554; P = 0.05) and IL-6 (r = 0.495; P = 0.07) levels.

CONCLUSIONS

Rifaximin improves cirrhosis-related thrombocytopenia and this could be related with the reduction of endotoxaemia.

Thrombocytopenia is more severe in patients with advanced chronic hepatitis C than B with the same grade of liver stiffness and splenomegaly

BACKGROUND AND AIM

The mechanism responsible for thrombocytopenia in chronic liver diseases (CLD) is not yet fully understood. The prevalence of thrombocytopenia has been reported to be higher in patients with hepatitis C virus-related hepatocellular carcinoma (CLD-C) than in those with hepatitis B virus-related hepatocellular carcinoma (CDC-B). We have examined the potential difference in thrombocytopenia between patients with CLD-B and those with CLD-C in terms of liver fibrosis adjustment and splenomegaly.

METHODS

The study cohort consisted of 102 patients with CLD-B and 143 patients with CLD-C were enrolled. Liver stiffness, which is reported to be well correlated with the degree of liver fibrosis, was measured by transient elastography.

RESULTS

The analysis of covariance with liver stiffness as a covariate revealed that the platelet count was lower in CLD-C patients than in CLD-B patients. Following stratification for liver stiffness, thrombocytopenia was found to be more severe in CLD-C patients than CLD-B patients with advanced liver stiffness, whereas the degree of splenomegaly was not significantly different. The plasma thrombopoietin level was not different between CLD-B and CLD-C patients with advanced liver stiffness, and the immature platelet number was lower in CLD-C patients despite thrombocytopenia being more severe in these patients.

CONCLUSIONS

CLD-C patients with advanced liver stiffness presented with more severe levels of thrombocytopenia than CLD-B patients even with the same grade of splenomegaly. Impaired platelet production rather than enhanced platelet destruction may underlie the mechanism responsible for thrombocytopenia in patients with CLD.

Evaluation of platelet kinetics in patients with liver cirrhosis: similarity to idiopathic thrombocytopenic purpura

BACKGROUND

Thrombocytopenia is a common manifestation of liver cirrhosis (LC), but its underlying mechanism is not fully understood. The purpose of the present paper was to evaluate the platelet kinetics in LC patients by examining several non-invasive convenient markers.

METHODS

Fifty-seven LC patients, 32 patients with idiopathic thrombocytopenic purpura (ITP), 12 with aplastic anemia (AA), and 29 healthy individuals were studied. Plasma thrombopoietin was measured by enzyme-linked immunosorbent assay. Absolute reticulated platelet (RP) count and plasma glycocalicin were used as indices for thrombopoiesis, and the indices for platelet turnover were the RP proportion and the plasma glycocalicin normalized to the individual platelet count (GCI).

RESULTS

There was no difference in thrombopoietin levels between LC patients and healthy controls. The RP proportion and GCI were significantly higher and the absolute RP count and glycocalicin significantly lower in LC patients than in healthy controls. These markers in ITP and LC patients were comparable, but significantly different from those in AA patients. The bone marrow megakaryocyte density in LC and ITP patients was similar, and significantly higher than in AA patients.

CONCLUSIONS

Cirrhotic thrombocytopenia is a multifactorial condition involving accelerated platelet turnover and moderately impaired thrombopoiesis. Thrombopoietin deficiency is unlikely to be the primary contributor to cirrhotic thrombocytopenia.

Review article: thrombocytopenia in chronic liver disease and pharmacologic treatment options

In patients with liver disease, thrombocytopenia is a clinical feature that may represent an obstacle to invasive diagnostic or therapeutic procedures, chemotherapy, and anti-viral treatment. Stimulation of the bone marrow is the most promising therapeutic intervention for thrombocytopenia in patients with chronic liver disease. The description of thrombopoietin and its (de)regulation in patients with chronic liver disease have disclosed new treatment opportunities. Indeed, pharmacologic treatment options for thrombocytopenia can be divided into treatments targeted at the thrombopoietin receptor (synthetic thrombopoietins and thrombopoietin-mimetic agents), and use of cytokines with general thrombopoietic potential. Unfortunately, use of synthetic thrombopoietin was hampered by the development of neutralizing antibodies, and thrombopoietin mimetic agents have not yet entered clinical studies. Interleukin-11 proved to be useful in increasing platelet count in patients with chronic liver disease, although its use is limited by side-effects. Erythropoietin has shown promising results in improving thrombocytopenia in cirrhotic patients. In patients with chronic liver disease, safe and well-tolerated treatments aimed at improving thrombocytopenia are still lacking. Larger studies are needed to evaluate and better characterize the thrombopoietic potential of erythropoietin. Human studies with thrombopoietin-mimetic agents are eagerly awaited in order to assess both effectiveness and safety of these drugs.

The role of thrombopoietin in the thrombocytopenia of patients with liver cirrhosis

OBJECTIVES

Thrombocytopenia is a common disorder among cirrhotics that has been traditionally explained by splenic platelet pooling and destruction. Thrombopoietin (TPO), the main stimuli for thrombopoiesis is produced primarily in the liver and degraded by circulating platelets, but its role in the thrombocytopenia of liver cirrhosis is not well understood. The main goal of this study is to clarify the role of TPO in the pathogenesis of thrombocytopenia in cirrhosis.

METHODS

The relation among TPO, platelet count, spleen size, portal hypertension, and liver function was studied in 33 cirrhotic patients before and after either partial splenic embolization or liver transplantation.

RESULTS

Cirrhotics with thrombocytopenia had lower serum TPO levels than healthy controls (median values (interquartile range: ICR) were 120.7 (42.0-191.6) vs 756.4 (527.0-965.1) pg/mL, respectively; p<0.001). Among cirrhotics with thrombocytopenia, serum TPO was related to spleen size (rho=-0.387, p=0.046), but not to platelet count as occurs physiologically. After partial splenic embolization, TPO and platelet count increased significantly and the physiological relation between TPO and platelet count was restored (rho=-0.665, p=0.026). Similar results were observed after liver transplantation.

CONCLUSIONS

Our results suggest that besides impaired production in the failing liver, an increased TPO degradation by platelets sequestered in the congested spleen may contribute to thrombocytopenia in cirrhotic patients.

Relationship between thrombopoietin serum levels and liver function in patients with chronic liver disease related to hepatitis C virus infection

OBJECTIVES

Thrombopoietin (Tpo) is an important regulator of megakaryocyte maturation and platelet production, and is mainly produced by the liver. A decrease in Tpo production is partly responsible for the thrombocytopenia observed in patients with chronic liver disease (CLD). The aim of this study was to evaluate the relationship between Tpo serum levels and liver function in patients with CLD related to hepatitis C virus (HCV) infection.

METHODS

We studied 37 patients with various degrees of HCV-related CLD. Of the patients, 17 had chronic hepatitis and 20 liver cirrhosis. Liver function was evaluated in all patients by the following hepatic blood flow dependent and independent tests that explore various hepatic metabolic functions: carbon-13 (13C)-aminopyrine breath test (13C-ABT), 13C-galactose breath test (13C-GBT), and monoethylglycinexylidide (MEGX) test. Liver function tests results were correlated with Tpo serum levels.

RESULTS

Tpo serum levels were significantly lower in patients with liver cirrhosis (88 +/- 23 pg/ml) as compared to those in patients with chronic hepatitis (128 +/- 55 pg/ml, p=0.0031). However, they did not correlate with serum albumin, bilirubin, or prothrombin activity. Tpo serum levels showed a significant positive correlation with 13C-ABT results (hourly dose at 30 min, rs=0.489, p=0.002; cumulative dose at 120 min, rs=0.425, p=0.008). Moreover, they showed a fair, positive correlation with 13C-GBT hourly dose at 30 min (rs=0.366, p=0.028), and a trend toward a positive correlation with the various MEGX test sampling times (MEGX15, rs=0.314, p=0.059; MEGX30, rs=0.284, p=0.088; and MEGX60, rs=0.320, p=0.059).

CONCLUSIONS

In this study we have shown that a progressive decline in liver function in patients with HCV-related CLD is paralleled by a decrease in Tpo production. The different correlations observed between Tpo and the various liver function tests suggests that this finding is mainly the result of a decrease in hepatic functional mass rather than dependent on alteration in splanchnic hemodynamic.

Platelet count increase following phlebotomy in iron overloaded patients with liver cirrhosis

Thrombocytopenia is a frequent hematological complication in patients with liver cirrhosis, but its pathogenesis is not clearly understood. We evaluated the effect of iron depletion by phlebotomy on platelet count in 62 consecutive iron overloaded patients with liver cirrhosis and thrombocytopenia. After a median follow-up of 30.2 months we observed a significant increase of platelet count in all patients (from mean baseline levels of 110.1 up to 168.22109/l at the end of follow-up, P<0.001) with platelet count normalization in 42 of them (67.7%). In addition, we observed a significant improvement of serum ALT levels (from pretreatment mean values of 126.7 up to 59.7 U/l at the end of follow-up, P<0.001) along with the reduction of serum ferritin levels and transferrin saturation during phlebotomy. Different pathogenetic mechanisms involving both humoral (erythropoietin and thrombopoietin, TPO) and physical (portal hypertension and hypersplenism) factors are here discussed to explain the platelet count increase following phlebotomy. Our results show that phlebotomy is effective not only in lowering iron overload, but also in improving liver function and thrombocytopenia in patients with liver cirrhosis.

A role of autoantibody-mediated platelet destruction in thrombocytopenia in patients with cirrhosis

Thrombocytopenia is a common manifestation in patients with liver cirrhosis (LC), but its underlying mechanism remains controversial. This study examined the role of anti-platelet autoimmunity in cirrhotic thrombocytopenia by determining the autoantibody response to GPIIb-IIIa, a major platelet surface autoantigen recognized by anti-platelet antibodies in patients with idiopathic thrombocytopenic purpura (ITP). Circulating B cells producing anti-GPIIb-IIIa antibodies as well as platelet-associated and plasma anti-GPIIb-IIIa antibodies were examined in 72 patients with LC, 62 patients with ITP, and 52 healthy controls. In vitro anti-GPIIb-IIIa antibody production was induced in cultures of peripheral blood mononuclear cells (PBMCs) by stimulation with GPIIb-IIIa. The frequency of anti-GPIIb-IIIa antibody-producing B cells in patients with LC was significantly greater than in healthy controls (10.9 +/- 6.2 vs. 0.4 +/- 0.3/10(5) PBMCs; P <.0001) and was even higher than the frequency in patients with ITP (8.2 +/- 5.2; P =.007). Anti-GPIIb-IIIa antibodies in the patients with LC and ITP were mainly present on the surfaces of circulating platelets rather than in the plasma in an unbound form. Furthermore, PBMCs from patients with LC and ITP produced anti-GPIIb-IIIa antibodies on antigenic stimulation with GPIIb-IIIa in vitro, and the specific antibodies produced had the capacity to bind normal platelet surfaces. In conclusion, the similar profile of the anti-GPIIb-IIIa autoantibody response in patients with LC and ITP suggests that autoantibody-mediated platelet destruction may contribute at least in part to cirrhotic thrombocytopenia.

Thrombopoietin in acute liver failure

Thrombopoietin (TPO) is the primary regulator of platelet production. TPO is produced in the liver and levels are low in patients with cirrhosis. Because thrombocytopenia is common in patients with acute liver failure (ALF), we measured TPO concentrations (normal TPO range, 31 to 136 pg/mL) in 51 patients with ALF to determine if low levels were associated with thrombocytopenia. TPO levels from hospital day 2 were elevated in 43% of patients, normal in 47%, and decreased in 10% of patients. Levels were higher in acetaminophen-induced than in non-acetaminophen-induced ALF, 160 (12 to 549) pg/mL versus 73 (18 to 563) pg/mL, respectively, P =.031. TPO levels did not correlate with platelet count and were not related with survival or infection. We analyzed daily TPO levels for the first week of hospitalization in 12 patients with acetaminophen-induced ALF and observed a gradual increase from a median admission level of 50 (5 to 339) pg/mL to a median peak level of 406 (125 to 1,081) pg/mL occurring on day 5 (3 to 6). Platelets were reduced in 11 of the 12 patients with a nadir platelet count of 52 (19 to 156) x 10(9) cells/L occurring on day 5.5 (1 to 6). The peak TPO level did not correlate with the nadir platelet count (P =.43). In conclusion, the normal inverse relationship between platelet count and TPO levels was not observed in ALF. Despite severe hepatic dysfunction, serum TPO levels were initially normal and increased during hospitalization in acetaminophen-induced ALF, but did not prevent the development of thrombocytopenia.

Serum thrombopoietin levels are linked to liver function in untreated patients with hepatitis C virus-related chronic hepatitis

BACKGROUND

Thrombocytopenia can be found in patients with chronic hepatitis related to hepatitis C virus (HCV). Both hypersplenism and decreased liver production of thrombopoietin (TPO) have been hypothesized as mechanisms responsible for thrombocytopenia.

AIMS

To assess the presence of relationships among platelet count, spleen size, TPO serum levels, liver histology, and liver function in a group of patients with HCV-related chronic hepatitis.

METHODS

Platelet count, TPO serum levels, and spleen size were assessed in 25 untreated HCV positive chronic hepatitis patients undergoing liver biopsy. These parameters were correlated to liver histology and liver function as evaluated by means of [(13)C]aminopyrine breath test (ABT).

RESULTS

Both platelet counts (146 +/- 48 vs. 202 +/- 56 x 10(9)/1, P < 0.03) and TPO serum levels (103 +/- 24 vs. 158 +/- 7 1 pg/ml, P < 0.02) were lower among patients with high fibrosis scores as compared to patients with low fibrosis scores. Patients with thrombocytopenia as well as patients with high fibrosis scores had lower ABT results as compared to patients with normal platelet counts and patients with no or mild fibrosis, respectively. TPO serum levels were correlated to platelet count (r(s) = 0.493, P = 0.016), and negatively correlated to fibrosis stage (r(s) = -0.545, P = 0.008). Lastly, low TPO serum levels were associated to a decrease in liver function.

CONCLUSIONS

Our study showed that in patients with chronic hepatitis related to HCV infection serum TPO levels are correlated to liver functional impairment and to the degree of liver fibrosis.

Plasma thrombopoietin in patients with cavernous transformation of the portal vein

Thrombopoietin (TPO), the primary regulator of thrombopoiesis, is produced mainly in the liver. Previous studies investigating blood TPO in chronic liver diseases revealed conflicting results. It has been suggested that hepatic TPO production is regulated by the portal blood supply to the liver. However, the role of TPO in the pathobiological basis of idiopathic portal vein thrombosis (PVT) and cavernous transformation of the portal vein (CTPV) has not been elucidated. The objective of this study is to assess plasma TPO concentrations in patients with CTPV. Eleven patients (4 men and 7 women, aged 38+/-12 years) with CTPV were studied. Sixteen healthy adults served as the control group (8 men and 8 women, aged 34+/-12 years). Median plasma TPO concentration was 326 pg/mL (range, 15-1402 pg/mL) in the patients with CTPV and 62.65 pg/mL (range, 38.5-102 pg/mL) in the control group (P = .003). In this study, we found significantly higher TPO concentrations in the plasma of patients with CTPV. The higher concentrations could be a result of the altered portal hemodynamics due to thrombosis. Moreover, TPO release by activated platelets might lead to the subsequent propagation of thrombosis in PVT.

The role of the liver in the production of thrombopoietin compared with erythropoietin

The liver plays an important role in the production of haemopoietic hormones. It acts as the primary site of synthesis of erythropoietin (EPO) in the fetal stage, and it is the predominant thrombopoietin (TPO)-producing organ for life. In contrast to that of EPO and other liver proteins, the hepatic synthesis of TPO is influenced little by external signals. Hepatocytes express the TPO gene in a constitutive way, i.e. irrespective of the level of platelets in blood. Megakaryocytes and platelets remove the hormone from blood by means of their high-affinity TPO receptors. Normally, the plasma level of TPO is relatively low ( approximately 10(-12) mol/l). However, in thrombocytopenic states due to marrow failure or bleeding, the concentration of circulating TPO may increase greatly. The simple feedback regulation by TPO and its target cells is efficient in maintaining constant platelet numbers in healthy people. Persisting thrombocytopenia develops only in severe liver or marrow failure. On the other hand, an increase in circulating TPO and interleukin 6 (IL-6) may cause reactive thrombocytosis in inflammatory diseases, including cancer. The indications for recombinant human thrombopoietin (rHuTPO) therapy and its impact on transfusion medicine are still under investigation.

Measurement of thrombopoietic levels: clinical and biological relationships

Platelet production is primarily regulated by the thrombopoietic cytokine thrombopoietin (TPO). In most cases thrombopoietin serum levels are determined by the rate of c-mpl receptor-mediated degradation after TPO uptake into platelets and megakaryocytes. The contribution of increased TPO protein synthesis by a translational mechanism was recently appreciated as the cause for hereditary thrombocythemia and will have to be elucidated in other conditions of thrombocytosis in association with increased TPO levels.