title: Alterations in the insulin-like growth factor system during the menstrual cycle in normal women.
abstract: 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.
authors.affiliation: Department of Oncology, Haukeland University Hospital, Bergen, Norway.
authors.forename: S I
authors.initials: SI
authors.lastname: Helle
authors.forename: G B
authors.initials: GB
authors.lastname: Anker
authors.forename: K A
authors.initials: KA
authors.lastname: Meadows
authors.forename: J M
authors.initials: JM
authors.lastname: Holly
authors.forename: P E
authors.initials: PE
authors.lastname: Lønning
mesh_terms: 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
chemical_list: 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