Effect of oestrogen status on serum levels of growth hormone-binding protein and insulin-like growth factor-I in non-pregnant and pregnant women.
OBJECTIVE
Since there appears to be a relationship between circulating oestrogens and growth hormone, we have investigated the effect of the oestrogen status of adult women on serum levels of GHBP and IGF-I.


METHODS
The investigation was performed on serum samples of 14 spontaneously menstruating women, 10 women taking oral contraceptives containing 20-50 micrograms ethinyloestradiol, and 30 pregnant women at different stages of pregnancy.


METHODS
Serum levels of GHBP were measured by HPLC gel filtration and IGF-I levels were measured by RIA after acid-ethanol extraction.


RESULTS
In the spontaneously menstruating women the mean +/- SD serum level of GHBP was 34.6 +/- 6.7% and of IGF-I 30 +/- 7 nmol/l. Serum GHBP levels were negatively (r = -0.67; P < 0.01) and IGF-I levels were positively related (r = 0.69; P < 0.01) to serum oestradiol concentrations. In the women taking oral contraceptives serum levels of GHBP were 47.0 +/- 7.4%. This was significantly (P < 0.001) higher than in spontaneously menstruating women. In contrast, IGF-I levels were not different from those obtained in spontaneously menstruating women. In the pregnant women, the mean +/- SD serum level of GHBP was not different from that observed in non-pregnant spontaneously menstruating women. Polynomial regression analysis, however, showed a significant (P = 0.01) second-order relationship between the duration of pregnancy and serum GHBP levels, with increasing levels during the first half of pregnancy and decreasing levels thereafter. Serum concentrations of IGF-I increased during the second half of pregnancy and were significantly (P < 0.005) elevated in the third trimester.


CONCLUSIONS
In non-pregnant women the endogenous oestrogen status seems to modulate negatively GHBP levels and positively IGF-I levels, whereas oral oestrogen administration, in contrast, increases serum levels of GHBP without modification of IGF-I levels. During pregnancy serum GHBP levels increase slightly during the first half of pregnancy and decrease thereafter, whereas IGF-I concentrations increase during the second part of pregnancy. The oestrogen status of women has a complex effect on serum concentrations of GHBP and IGF-I and has therefore to be taken into account when evaluating serum levels of GHBP and IGF-I.
Massa
G
G
Department of Paediatrics, University of Leuven, Belgium.
Igout
A
A
Rombauts
L
L
Frankenne
F
F
Vanderschueren-Lodeweyckx
M
M
D000284:Administration, Oral; D000328:Adult; D002352:Carrier Proteins / Q000097:blood*; D004958:Estradiol / Q000097:blood; D004967:Estrogens / Q000097:blood*; D004997:Ethinyl Estradiol / Q000008:administration & dosage; D005260:Female; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008598:Menstruation / Q000097:blood; D011247:Pregnancy / Q000097:blood*
D002352:Carrier Proteins; D004967:Estrogens; D004997:Ethinyl Estradiol; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; C051815:somatotropin-binding protein