Quantitative determination of the binding capacity of the sex hormone-binding globulin, using agar gel electrophoresis.

An easy, rapid and precise technique for the determination of the binding capacity of the sex hormonebinding globulin (SHBG) is described. The plasma is incubated with [3H]5 alpha-dihydrotestosterone (DHT) either alone, or together with an excess of unlabelled DHT. The SHBG-binding peaks are demonstrated by agar gel electrophoresis according to Wagner (1972) Hoppe-Seylers Z. Physiol. Chem. 353, 1235--1245), and the SHBG-binding capacity is calculated from the radioactivity specifically bound to the SHBG peak, corrected for the dissociation of the [3H]DHT from SHBG during the 90 minute electrophoresis. In addition to investigating various problems of methodology, the following clinical results were obtained: 1 Normal range (x +/- s) of the SHBG-binding capacity for males (age 22--41; n = 26) 38 +/- 11 nmol/1.2. An older male group has, with 48 +/- 10 nmol/l, a a significantly higher binding capacity. 3. The highest values found so far were in pregnancy plasma of the third trimenon (330 and 400 nmol/l).