Serum and urinary estrone sulfate during the menstrual cycle, measured by a direct radioimmunoassay, and fate of exogenously injected estrone sulfate

Serum and early-morning urinary levels of estrone sulfate during the menstrual cycle were measured by a direct radioimmunoassay without hydrolysis. These levels were high and showed prominent peaks [serum, 2.67 ± 0.37 ng/ml (mean ± SE); urine, 5.82 ± 2.3 µg/l] around the day of the preovulatory estradiol-17β peak, and increased again during the luteal phase. Following intravenous injection of estrone sulfate, serum estrone sulfate, estrone and estradiol-17β were measured. The conversion of estrone sulfate to estrone and/or estradiol-17β was very small during their transit in the general circulation.