title: Genetic and environmental components of interindividual variation in circulating levels of IGF-I, IGF-II, IGFBP-1, and IGFBP-3.
abstract: We assessed the magnitude of the genetic component in the variation of circulating levels of insulin-like growth factors I and II (IGF-I and IGF-II), and their binding proteins IGFBP-1 and IGFBP-3 by measuring their serum concentrations in 32 monozygotic and 47 dizygotic adult twin pairs of the same sex. The intrapair correlation for the IGF-I levels was r = 0.41 (P < 0.009) for monozygotic twins and r = 0.12 (P < 0.22) for dizygotic twins. For the IGF-II concentration the intrapair correlations were r = 0.66 (P < 0.0001) for the monozygotic and r = 0.34 (P < 0.01) for the dizygotic twins. No significant intrapair correlation was found for IGFBP-1 levels in either group. The correlations for IGFBP-3 concentration were r = 0.65 (P < 0.0001) and r = 0.23 (P < 0.06) for monozygotic and dizygotic twins, respectively. Women had higher IGF-II levels than men (635+/-175 vs. 522+/-144 microg/liter; P < 0.0001) and IGFBP-3 levels were also higher in women compared with men (5441+/-1018 vs. 4496+/-1084 microg/liter; P < 0.001). The proportion of variance attributable to genetic effects was 38% for the IGF-I concentration, 66% for the IGF-II concentration, and 60% for the IGFBP-3 concentration. No significant heritability was found for the IGFBP-1 concentrations. Our results show that, in adults, there is a substantial genetic contribution responsible for interindividual variation of the circulating levels of IGF-I, IGF-II, and IGFBP-3, but not for the IGFBP-1 levels.
authors.affiliation: Department of Obstetrics and Gynecology, Helsinki University Central Hospital, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Harrela
authors.forename: H
authors.initials: H
authors.lastname: Koistinen
authors.forename: J
authors.initials: J
authors.lastname: Kaprio
authors.forename: M
authors.initials: M
authors.lastname: Lehtovirta
authors.forename: J
authors.initials: J
authors.lastname: Tuomilehto
authors.forename: J
authors.initials: J
authors.lastname: Eriksson
authors.forename: L
authors.initials: L
authors.lastname: Toivanen
authors.forename: M
authors.initials: M
authors.lastname: Koskenvuo
authors.forename: P
authors.initials: P
authors.lastname: Leinonen
authors.forename: R
authors.initials: R
authors.lastname: Koistinen
authors.forename: M
authors.initials: M
authors.lastname: Seppälä
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D005260:Female; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood* / Q000235:genetics; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood* / Q000235:genetics; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012727:Sex Characteristics; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic
chemical_list: D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II