An in vivo system in man for quantitation of estrogenicity. I. Physiologic changes in binding capacity of serum corticosteroid-binding globulin.
A modified method of measuring the binding capacity of corticosteroid-binding globulin (CBG-BC) in serum using 3H-cortisol saturation-charcoal adsorption is described. Forty serum samples per day can be assayed in duplicate, each sample with a heated nonspecific binding blank (60 degrees C.). The interassay coefficient of variation is less than 6 per cent. All age groups of men and women had similar levels of CBG-BC, except postmenopausal women, whose levels were higher (15.9 +/- 0.2 vs. 18.7 +/- 0.8 microgram per 100 ml., mean +/- standard error of the mean, respectively; z = -3.51, p less than 0.001). The variance of serum levels of CBG-BC throughout the menstrual cycle in five women was small (coefficient of variation = 13 per cent) and showed no relationship to the marked and cyclic changes in estradiol levels (coefficient of variation = 73 per cent). In pregnancy the levels of CBG-BC increased linearly after estradiol levels exceeded 1,300 pg. per milliliter and after estrone levels exceeded 500 pg. per milliliter (r = 0.88, p less than 0.001; and r = 0.85, p less than 0.001, logarithmic regression analysis). The findings of this study indicate that serum levels of CBG-BC are relatively constant in men and menstruating women. In pregnancy after a high threshold of endogenous estrogen is reached, CBG-BC increases in a direct dose-response manner as levels of estradiol increase further.
D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004958:Estradiol / Q000097:blood*; D005260:Female; D006801:Humans; D006854:Hydrocortisone; D008297:Male; D008593:Menopause; D008598:Menstruation; D011247:Pregnancy; D011786:Quality Control; D014156:Transcortin / Q000032:analysis*
D004958:Estradiol; D014156:Transcortin; D006854:Hydrocortisone