Erythrocytosis after renal transplantation represents an abnormality of insulin-like growth factor-I and its binding proteins.
BACKGROUND
Secondary erythrocytosis is classically defined by an increase in erythropoietin (EPO) production. Despite increased levels of EPO often seen in secondary erythrocytosis, some of these forms such as that seen after renal transplantation remain undefined. Our group has recently investigated the in vivo function of insulin-like growth factor-I (IGF-I) in erythropoiesis both in humans and in a murine model of chronic renal failure. These data, and the recently recognized role of IGF-I in polycythemia vera, suggested that IGF-I might be involved in secondary erythrocytosis.


METHODS
Renal transplant recipients who developed erythrocytosis after transplantation were compared to normal individuals and to renal transplant recipients without erythrocytosis. We measured fasting serum EPO and IGF-I in all three groups. Because binding proteins may modify IGF-I function, IGF-I-binding proteins (IGFBP) 1 and 3, major binding proteins of IGF-I, were also measured.


RESULTS
Renal transplant recipients have significantly elevated serum of IGF-I and IGFBP3 compared to normal individuals. When transplant recipients with and without posttransplant erythrocytosis were compared, similar levels of IGF-I were found; however, the group with erythrocytosis had significantly elevated IGFBP1 and IGFBP3. No other significant differences including EPO levels were found between the groups.


CONCLUSIONS
Erythrocytosis after renal transplantation represents an anomaly of both IGF-I and its major binding proteins. Further studies are under way to better define this dysregulation and determine whether IGF-I can play a more generalized role in secondary forms of erythropoiesis.
Brox
A G
AG
Division of Hematology, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada.
Mangel
J
J
Hanley
J A
JA
St Louis
G
G
Mongrain
S
S
Gagnon
R F
RF
D000328:Adult; D000368:Aged; D004921:Erythropoietin / Q000097:blood; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D007328:Insulin / Q000097:blood; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000502:physiology*; D016030:Kidney Transplantation; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D011086:Polycythemia / Q000097:blood / Q000209:etiology* / Q000503:physiopathology; D011183:Postoperative Complications
D007166:Immunosuppressive Agents; D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D004921:Erythropoietin; D007334:Insulin-Like Growth Factor I