THE OVARIAN PRODUCTION OF A PREGNANETRIOL PRECURSOR

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Abstract
SUMMARY: During the normal menstrual cycle the excretion of pregnanetriol increased on the day that the excretion of oestrone and oestradiol reached a maximum during the follicular phase. Pregnanediol excretion did not begin to increase until 2 days later. The excretion of pregnanetriol reached a peak and began to decrease before that of pregnanediol. Thus the pattern of pregnanetriol excretion was different from that of the excretion of oestrogens or pregnanediol. Progestational steroids in a dose which inhibited ovulation prevented the rise in both pregnanetriol and pregnanediol excretion during the second half of the menstrual cycle. The administration of oestradiol dibenzoate to two subjects did not affect pregnanetriol excretion. It is suggested that the increased amounts of pregnanetriol excreted during the second half of the menstrual cycle arise from a precursor of pregnanetriol, most probably 17α-hydroxyprogesterone, secreted by the ovary.