Non-protein-bound oestrogens in plasma and urinary excretion of unconjugated oestrogens in men

Unconjugated oestrone and unconjugated oestradiol-17 beta were measured in 24 h urine specimens from twenty normal men. The concentrations of non-protein-bound oestrone and non-protein-bound oestradiol-17 beta, in samples of blood obtained from these subjects during the time in which the urine was collected, were measured by equilibrium dialysis (using a correction for plasma dilution). The mean excretion of unconjugated oestrone (0.44+/- 0.36 nmol/24 h, mean +/- SD) was significantly greater (Pless than 0.01) than that of unconjugated oestradiol-17 beta (0.20 +/- 0.13 nmol/24 h). The concentrations of non-protein-bound oestrone and non-protein-bound oestradiol-17 beta in plasma were 5.52 +/- 2.69pmol/1 and 2.42 +/- 0.73 pmol/1, respectively. There was no correlation between the quantity of unconjugated oestrone excreted and the concentration of non-protein-bound oestrone in plasma (r=0.27) nor between the quantity of unconjugated oestradiol-17 beta in the urine and the concentration of non-protein-bound oestradiol-17 beta in plasma (r=0.05). Therefore in normal men, estimation of unconjugated oestrone or oestradiol-17 beta in urine provides no guide to the concentration of the corresponding non-protein-bound oestrogen in plasma.