A simplified method for measuring the binding capacity of sex hormone-binding globulin in human serum and its clinical application (author's transl)

Abstract

A simple and reliable method for determining the binding capacity of the sex hormone-binding globulin (SHBG-BC) in human serum is described. The principle of this method is to saturate the SHBG binding sites with dihydrotestosterone (DHT) and measure the amount of SHBG-bound steroid. Endogenous steroids are initially removed from the serum samples by adsorption on dextran-coated charcoal. The samples are subsequently equilibrated with a mixture of known amount of tritium-labeled and unlabeled DHT. The unbound steroid is removed by dextran-coated charcoal incubated at 4 degrees C, and the mass of bound DHT is determined from the known specific activity of the added steroid. The intraassay and interassay coefficient of variation of this assay method is less than 6.2% and 7.5%, respectively. Forty serum samples can be assayed in duplicate in a working day. The mean values of SHBG-BC, expressed as microgram DHT bound per 100ml serum, were 1.56 +/- 0.33 (SD) in 6 adult men aged 20 approximately 40 and 2.05 +/- 0.75 in 37 adult women aged 20 approximately 36. Higher levels (1.75 +/- 0.40) were found in 10 older men aged 65 approximately 80. In contrast, SHBG-BC (1.80 +/- 0.30) in postmenopausal women (ages 52 approximately to 62) was lower than that in the reproductive age group of women. No significant variations in SHBG-BC were observed during the normal menstrual cycle. The levels of SHBG-BC rose progressively in pregnancy to 9 approximately 10 times those in the normal non-pregnant women. In 4 women with polycystic ovarian disease and 2 hirsute women, SHBG-BC levels were lower (means: 1.63 and 0.75, respectively), while patients with 1st and 2nd grade amenorrhea showed levels similar to those in the reproductive women.