Quantitative determination of sex hormone-binding globulin capacity in the plasma of normal and diabetic pregnancies.

Abstract Sex hormone-binding globulin (SHBG) capacity was measured in a longitudinal study in plasma samples from normal subjects, diabetics, and gestational diabetics throughout pregnancy, together with unconjugated plasma estradiol. In normal women SHBG capacity (expressed in ng DHT bound per ml of plasma) increased from 23.7 ± 13.7 (SD) in the 5–8th week period, to 74.5 ± 20.7 in the 17–20th week period, and to 102 ± 24 in the 37–40th week period. In diabetics the SHBG capacity for the same periods of time were respectively: 25.3 ± 17.2, 83.1 ± 29.1, and 111.6 ± 22.6. Plasma levels of unconjugated estradiol were 55% higher in the diabetics than in the normal subjects in the second half of gestation, as reported in detail in another publication.1 From the imbalance between the close to normal SHBG capacity and the higher plasma levels of unconjugated estradiol in the diabetics, it is suggested that the unbound, i.e., metabolically active, fraction of plasma estradiol reaches higher levels in diabetics t...