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  • Title: Studies on ovarian and adrenal steroids at different phases of the menstrual cycle: II. A comparative assessment of the circadian variation in steroid and lutropin levels during the follicular, periovulatory and luteal phases.
    Author: Aedo AR, Landgren BM, Diczfalusy E.
    Journal: Contraception; 1981 Apr; 23(4):407-24. PubMed ID: 7273761.
    Abstract:
    In six normally menstruating women, ovarian and adrenal steroids and biologically active lutropin (LH) were measured in peripheral plasma samples collected every 3 h. during a period of 39 h. in the early follicular phase, periovulatory period or luteal phase of three consecutive cycles. The purpose of the study was to assess the influence of the phases of the cycle on the diurnal variation in the levels of different steroids and lutropin following the elimination of the between subject variation. Cortisol, 17-hydroxypregnenolone, dehydroepiandrosterone and androstenedione showed a marked circadian rhythm in all three phases of the cycle. No changes in the levels of cortisol, 17-hydroxypregnenolone and dehydroepiandrosterone with the phase of the cycle were observed when the "morning" samples were considered; however, when the "evening" samples were analyzed, the levels of these steroids were higher in the luteal phase than in the follicular phase. As a result of this increase, the amplitude of the circadian rhythm of these steroids considerably decreased in the luteal phase. The "morning" as well as the "evening" increase observed in the levels of androstenedione during the periovulatory period was not able to mask the circadian rhythm. A circadian rhythm in pregnenolone, 17-hydroxyprogesterone, testosterone, and dihydrotestosterone levels was detected only in certain phases of the cycle. All these steroids showed a circadian rhythm in the early follicular phase. The rhythm of pregnenolone and 17-hydroxyprogesterone was still present in the periovulatory period but was no longer detectable in the luteal phase, meanwhile that of testosterone and dihydrotestosterone was not demonstrable neither in the periovulatory period nor in the luteal phase. Compared to the levels of the follicular phase, an increase in pregnenolone and 17-hydroxyprogesterone levels was observed in the periovulatory period which was followed by a further rise in the luteal phase. This increase completely masked the circadian rhythm in the luteal phase. An inverse circadian rhythm in lutropin levels was detected during the luteal phase. The "morning" values were lower than those found during the "evening" period. No such changes were observed in the other phases of the cycle. In none of the phases studied did the levels of progesterone or estradiol show any circadian variation. The data indicate that a circadian rhythm in the peripheral levels of a given steroid mainly depends on the relative contributions of the ovaries and adrenals and that these contributions exhibit major differences at the various phases of the cycles. It is concluded that - in contradistinction to the situation in the human male - in normally menstruating women, the peripheral levels of steroids of predominantly gonadal origin do not exhibit a circadian rhythmicity.
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