STUDIES ON THE PATTERN OF CIRCULATING STEROIDS IN THE NORMAL MENSTRUAL CYCLE

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Abstract
The plasma levels of estrone sulfate, estradiol sulfate, estrone and estradiol were studied in samples collected daily from 8 normally menstruating women throughout a complete menstrual cycle. In order to ascertain the normality of the cycles studied, LH [luteinizing hormone] and progesterone were also determined daily. All compounds were measured by radioimmunoassay, the sulfates after solvolysis. For the determination of the sulfates a procedure was developed which fulfilled the recognized criteria of reliability. Both estrone sulfate and estradiol sulfate displayed a marked cyclic pattern, similar to and correlated with that of estrone and estradiol, i.e., all 4 estrogens exhibited a marked mid-cycle peak and elevated levels during the luteal phase. The mean levels of the steroid moiety of estrone sulfate were 10-15 times higher than those of estrone, and 2-3 times higher than those of the 3 other estrogens together. On the other hand, the mean levels of estradiol sulfate were 1.2-4 times lower than those of estradiol. The ratios of the levels of various pairs of estrogens were calculated. All pairs showed a considerable change of ratios from the early follicular phase to mid-cycle. The mutual metabolic equilibria of estrogens are different in various phases of the cycle. Daily measurements of estrone sulfate and estradiol sulfate do not seem to provide a better index to predict the day of ovulation than the characteristic changes in progesterone and 17-hydroxyprogesterone levels.