A rapid method for the measurement of sex hormone binding globulin capacity of sera

A simple rapid method for the measurement of sex hormone binding globulin (SHBG) capacity, using 0.2ml of serum, is described. [4-¹⁴C] Testosterone is used as the saturating ligand at one dose level for all samples except pregnancy sera. Albumin bound [4-¹⁴C] testosterone is separated from the globulins with ammonium sulphate and the labelled globulin fraction counted. Pre-treatment of sera with a charcoal suspension under defined optimum conditions removes endogenous steroids associated with the binding proteins without affecting the binding [4-¹⁴C] testosterone to SHBG. The method shows good reproducibility with a coefficient of variation of 4% for male and 4.7% for female serum. Association constants measured for normal male, female and pregnancy sera were 3.6 × 10⁸ M^?1 , 3.2 × 10⁸ M^?1, and 1.7 × 10⁸ M^?1 at 20°, respectively.Normal males gave SHBG capacities of 5.0 ± 0.36 × 10^?8 M/1; females, 7.80 ± 1.24; prepubertal children, 7.01 ± 1.8. Women with amenorrhoea and hirsute women with polycystic ovaries had the lowest SHBG capacities of all, at 4.19 ± 0.75 and 4.06 ± 0.97 respectively. Post-menopausal women also had low levels, 5.25 ± 1.25. Five males with selective hypogonadotrophic hypogonadism had a mean value of 5.69 ± 0.84 which was significantly higher than the normal males. Two patients with Kallman's syndrome had elevated SHBG capacities. Two patients with panhypopituitarism and one patient with Klinefelter's syndrome had low SHBG capacities when compared with normal males. One patient with growth hormone deficiency had a normal SHBG capacity. Pregnancy sera had the highest capacities at 29.03 ± 3.76. No day to day variation in SHBG capacity could be demonstrated over a three day period in the sera from ten normal males.