Follicular fluid levels of insulin-like growth factor I, insulin-like growth factor binding protein I, and ovarian steroids collected during ovum pick-up.

OBJECTIVE

To evaluate interrelationships between levels of insulin-like growth factor I (IGF-I), insulin-like growth factor binding protein (IGFBP-I), and ovarian steroids in late preovulatory follicular fluid (FF) after pituitary desensitization with GnRH agonist and controlled ovarian hyperstimulation.

DESIGN

Follicular fluid and matched serum were collected during the ovum pick-up. Insulin-like growth factor binding protein I, E2, P, and androstenedione (A) were measured by means of RIA, whereas T was measured by means of fluoroimmunoassay and IGF-I by means of immunoradiometric assay.

SETTING

University teaching hospital.

PARTICIPANTS

Fifty-nine patients underwent 62 ovum pick-ups for IVF.

MAIN OUTCOME MEASURES

Levels of IGF-I, IGFBP-I, E2, P4 (representative of follicular maturity), T, and A in FF and the volume of this fluid were determined. Levels of E2 to A (representative of aromatase activity) in FF were examined in relation to the volume of FF.

RESULTS

Levels of FF-IGF-I decreased with increasing volume of FF. This observation is unprecedented. In contrast, FF-P increased with increasing volume of FF. The reverse relationships with FF volume between FF-IGF-I and FF-P may not be causal because no correlation was found between concentrations of FF-IGF-I and FF-P. Our findings are consistent with and complementary to those in previous reports. The follicular fluid E2:A ratio, FF-E2, FF-A, FF-T, and FF-IGFBP-I were not found to be correlated with volume of FF.

CONCLUSION

Decreased levels of FF-IGF-I with unaltered levels of FF-IGFBP-I in larger follicles may favor a shift toward diminished action of IGF-I at the time of immediate preovulation. The physiological significance of this shift remains uncertain as it is not reflected in the levels of steroids in FF.