The use of plasma or early morning urine specimens for monitoring estrogen in non-pregnant women.

A comparison was made of estradiol in plasma and estrogen in urine of non-pregnant women. Estradiol was measured in plasma by RIA and estrogen excretion in urine was calculated from estrogen and creatine levels in early morning urine samples. There was a close correlation of values obtained by the two methods and both gave consistently low values for a woman who apparently did not ovulate. Either plasma or single urine specimens were convenient for the women and suitable for monitoring estrogen levels. These methods, which require only a single sample each day, would be especially useful when multiple samples are required.