Longitudinal changes of insulin-like growth factors and their binding proteins throughout normal pregnancy.
BACKGROUND
Insulin-like growth factors (IGFs) are anabolic proteins that are essential regulators of cell division, differentiation and growth. We describe the longitudinal changes in IGF-I, IGF-II and the binding proteins IGFBP-1, -2 and -3 before and during normal pregnancy.


METHODS
Serum samples were taken before conception and then at 12, 24 and 36 weeks of gestation in 41 healthy women with uncomplicated pregnancies. We measured IGF-I using an automated chemiluminescent method, IGF-II and IGFBP-2 using in-house radioimmunoassays (RIAs), and IGFBP-1 and IGFBP-3 using commercial enzyme-linked immunosorbent assay (ELISA) and RIA kits, respectively. Because of the potential haemodilution effects during pregnancy, albumin was also measured in all samples.


RESULTS
There was a significant fall in IGF-I during the first (36%) and second trimesters (21%) followed by an increase of 25% at 36 weeks. During pregnancy, the mean IGF-II concentrations fell by 12% at 12 weeks, 8% at 24 and 8% at 36 weeks compared with pre-conception values. When IGF-II results were adjusted for the haemodilution of pregnancy, its concentrations increased. During pregnancy, there was a rapid increase in mean IGFBP-1 levels by 17-fold (12 weeks), 24-fold (24 weeks) and 25-fold (36 weeks). IGFBP-2 concentrations fell after conception but started to increase towards term. This increase was more significant when adjusted for haemodilution. In contrast, IGFBP-3 concentrations increased significantly throughout pregnancy.


CONCLUSIONS
Our data on the physiological changes of IGFs and their binding proteins add further evidence of the vital roles of these hormones throughout normal pregnancy.
Monaghan
John M
JM
Department of Clinical Chemistry, Nottingham City Hospital, Nottingham NG5 1PB, UK.
Godber
Ian M
IM
Lawson
Nigel
N
Kaur
Malveen
M
Wark
Gwen
G
Teale
Derrick
D
Hosking
David J
DJ
D015415:Biomarkers / Q000097:blood; D001724:Birth Weight; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005865:Gestational Age; D006438:Hemodilution; D006801:Humans; D007231:Infant, Newborn; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D008137:Longitudinal Studies; D008163:Luminescent Measurements; D008297:Male; D011247:Pregnancy / Q000097:blood*; D011863:Radioimmunoassay; D013002:Somatomedins / Q000032:analysis* / Q000378:metabolism; D013223:Statistics as Topic
D015415:Biomarkers; D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D013002:Somatomedins