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

Abstract

ABSTRACT The plasma levels of oestrone sulphate, oestradiol sulphate, oestrone and oestradiol 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 and progesterone were also determined daily. All compounds were measured by radioimmunoassay, the sulphates after solvolysis. For the determination of the sulphates a procedure was developed which fulfilled the recognized criteria of reliability. Both oestrone sulphate and oestradiol sulphate displayed a marked cyclic pattern, similar to and correlated with that of oestrone and oestradiol, i. e., all 4 oestrogens exhibited a marked mid-cycle peak and elevated levels during the luteal phase. The mean levels of the steroid moiety of oestrone sulphate were 10–15 times higher than those of oestrone, and 2–3 times higher than those of the 3 other oestrogens together. On the other hand, the mean levels of oestradiol sulphate were 1.2 to 4 times lower than those of oestradiol. The ratios of the levels of various pairs of oestrogens were calculated. All pairs showed a considerable change of ratios from the early follicular phase to mid-cycle. This demonstrates that the mutual metabolic equilibria of oestrogens are different in various phases of the cycle. Daily measurements of oestrone sulphate and oestradiol sulphate do not seem to provide a better index to predict the day of ovulation than the characteristic changes in progesterone and 17-hydroxyprogesterone levels.