Reduced free IGF-I and increased IGFBP-3 proteolysis in Turner syndrome: modulation by female sex steroids.
The bioactivity of the growth hormone-insulin-like growth factor (IGF) system is reduced in Turner syndrome and may explain the reduction seen in final height. We compared levels of free and total IGF-I, immunoreactive and Western ligand blot IGF-binding protein (IGFBP)-3, and IGFBP-3 proteolysis in women with Turner syndrome (n = 23) before (T(B)) and during 6 mo treatment with 17beta-estradiol and norethisterone. An age-matched group of controls (n = 24) was included. Total IGF-I and immunoreactive levels of IGFBP-3 were comparable in T(B) and controls, whereas free IGF-I (P = 0.02) in T(B) was less than in controls. Western ligand blotting (WLB)-IGFBP-3 was significantly lower in T(B) than in controls (P = 0.0005). Accordingly, IGFBP-3 proteolysis was greater in Turner syndrome (P = 0.001). Female sex steroid treatment increased WLB-IGFBP-3 (P = 0.0005), whereas immunoreactive IGFBP-3 and IGFBP-3 proteolysis were normalized (P = 0.004). Free IGF-I remained unchanged (P = 0.8), with a tendency toward a decrease in total IGF-I (P = 0.1). In conclusion, despite normal total IGF-I and immunoreactive IGFBP-3, free serum IGF-I is less and IGFBP-3 proteolysis is greater in Turner syndrome than in controls. During sex steroid treatment, IGFBP-3 proteolysis normalized, without any change in free IGF-I.
Gravholt
C H
CH
Medical Department M (Endocrinology and Diabetes) and Medical Research Laboratories, Aarhus University Hospital, DK-8000 Aarhus C, Denmark. ch.gravholt@dadlnet.dk
Frystyk
J
J
Flyvbjerg
A
A
Orskov
H
H
Christiansen
J S
JS
D000328:Adult; D001823:Body Composition; D004958:Estradiol / Q000627:therapeutic use; D005260:Female; D019382:Human Growth Hormone / Q000378:metabolism; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism*; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D009640:Norethindrone / Q000627:therapeutic use; D010447:Peptide Hydrolases / Q000378:metabolism*; D045167:Progesterone Congeners / Q000627:therapeutic use; D013002:Somatomedins / Q000032:analysis; D014424:Turner Syndrome / Q000188:drug therapy / Q000378:metabolism*
D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D045167:Progesterone Congeners; D013002:Somatomedins; D019382:Human Growth Hormone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D010447:Peptide Hydrolases; D009640:Norethindrone