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Insulin-Like Growth Factors in Amniotic Fluid^*

Department of Medicine, Division of Endocrinology and Metabolism, University of Florida Gainesville, Florida 32610
The Department of Obstetrics and Gynecology, University of Manitoba Winnipeg, Manitoba, Canada R3E 0W3

Address requests for reprints to: Dr. Thomas J. Merimee, Department of Medicine, University of Florida, Box J-226, JHMHC, Gainesville, Florida 32610.

The concentrations of insulin-like growth factors I and II (IGF-I and IGF-II) in amniotic fluid were determined by specific immunoassays in 58 women. IGF-I concentrations were constant throughout gestation at approximatey 20 ng/ml; the mean IGF-II concentration was 114 ± 13 (±SE) ng/ml at the earliest period of gestation studied and remained unchanged at 26 to 33 weeks despite a greater than 50% decrease in amniotic fluid total protein. A precipitous decrease in IGF-II concentration occurred at term which was not explainable by alterations in total amniotic fluid protein concentration. The concentrations of IGF-I and IGF-II in amniotic fluid did not correlate with concentrations of these factors in maternal serum (r = 0.08 and 0.09, respectively).

[¹²⁵I]IGF-I and [¹²⁵I]IGF-II, after incubation with amniotic fluid, bound to a 40–45 K protein (or proteins). A carrier protein of greater mol wt, as in serum, was not detected.

These findings indicate that there is dynamic control of IGF in amniotic fluid during normal pregnancy.

^* This work was supported by Grant AM-18130 from the NIAMDD, NIH, and grants from the Florida Citrus Commission and the General Clinical Research Center Program of the Division of Research Resources, (RR-00082).

Received May 23, 1984.

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