Inhibin in normal and abnormal pregnancy: maternal serum concentration and partial characterization.

OBJECTIVE

This study evaluated maternal serum inhibin concentration and molecular distribution in normal and abnormal pregnancies.

STUDY

DESIGN

Serum inhibin levels were measured by radioimmunoassay in 33 abnormal pregnancies (23 singleton and 10 multiple gestations) and 33 matched controls and were compared with pregnancy variables.

RESULTS

In the controls serum inhibin concentrations rose with gestational age (correlation coefficient 0.358, p < 0.01) and were higher in mothers with female fetuses (p < 0.05). Inhibin levels were higher in the abnormal singleton pregnancies (2.69 +/- 1.41 ng/ml) than in controls (1.26 +/- 0.32 ng/ml, p < 0.0001) and increased more rapidly with gestational age in multiple pregnancies (p < 0.05). Gel filtration chromatographic analysis of immunoreactive inhibin revealed three peaks with the major form having an apparent molecular weight of 55 to 60 kd.

CONCLUSION

Maternal serum inhibin concentrations are affected by gestational age, fetal gender, and complications of pregnancy. Most of the immunoreactive inhibin in maternal circulation is a large-molecular-weight form.