Distribution of 17 beta-estradiol in the sera of normal British and Japanese women.

Normal Japanese women had significantly more of their blood 17 beta-estradiol (E2) bound to sex hormone-binding globulin (SHBG) (53%) than British women (30%) and conversely less bound to albumin. While the proportion of SHBG-bound E2 increased with SHBG capacity and while binding fell as weight increased, the differences between the races do not appear to be explicable in terms of SHBG capacity or weight. At a given SHBG capacity, the Japanese women had more E2 bound to the protein than the British women. Where weights in the 2 populations overlapped, the Japanese women still had more of their E2 bound to SHBG than did the British women. Our results suggested that the affinity of albumin for E2 is lower in Japanese women.