Alterations in the insulin-like growth factor system during the menstrual cycle in normal women.
OBJECTIVE
To evaluate the effects of endogenous estrogens and progestins on the IGF-system during the normal menstrual cycle in healthy premenopausal women not using contraceptive drugs.


METHODS
Nine women had fasting blood samples obtained at 2-3 days intervals during a 5 week study period. Plasma levels of IGF-I, IGF-II, IGFBP-I, IGFBP-3, estradiol and progesterone were measured by radioimmunoassay (RIA) in each sample. IGFBP-3 was also evaluated by Western ligand blot (WLB) and immunoblot. Any differences between the menstrual phase (defined as day 1-5), follicular and luteal phases (separation based on plasma estradiol and progesterone values) were evaluated by the Friedman test.


RESULTS
A small but significant difference in plasma levels of IGF-I (P < 0.01) and IGFBP-d (P < 0.05) measured by RIA between the three phases were seen with the highest levels found during the follicular phase. No change in plasma levels of IGFBP-1 and IGF-II was found and immunoblots did not reveal any alteration in the ratio of fragmented to intact IGFBP-3 during the menstrual cycle. A positive correlation between plasma levels of IGF-I and estradiol was seen in 8 out of 9 patients (P = 0.012).


CONCLUSIONS
The finding of a slight but significant higher level of plasma IGF-I in the follicular and luteal phases compared with the menstrual phase suggests plasma estradiol may influence the level of this growth factor. This hypothesis is further supported by the finding of a correlation between plasma levels of IGF-I and estradiol but not progesterone in individual patients at different times during the menstrual cycle.
Helle
S I
SI
Department of Oncology, Haukeland University Hospital, Bergen, Norway.
Anker
G B
GB
Meadows
K A
KA
Holly
J M
JM
Lønning
P E
PE
D000328:Adult; D004958:Estradiol / Q000097:blood / Q000378:metabolism; D005260:Female; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood* / Q000378:metabolism; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood* / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000032:analysis* / Q000378:metabolism; D008597:Menstrual Cycle / Q000097:blood / Q000378:metabolism*; D008875:Middle Aged; D017697:Premenopause / Q000097:blood / Q000378:metabolism*; D011374:Progesterone / Q000097:blood / Q000378:metabolism; D011863:Radioimmunoassay
D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D011374:Progesterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II