Women's sexual experience during the menstrual cycle: identification of the sexual phase by noninvasive measurement of luteinizing hormone

Journal of Sex Research, Feb, 2004 by Susan B. Bullivant, Sarah A. Sellergren, Kathleen Stern, Natasha A. Spencer, Suma Jacob, Julie A. Mennella, Martha K. McClintock

Confirming Ovulation

Participants collected urine on days 5, 7, and 9 after the onset of the preovulatory LH surge to determine levels of pregnanediol-3-glucuronide. These were measured either by an enzyme immunoassay (ProgestURINE kit; Monoclonol Antibodies, Inc.) or radioimmunoassay. A functional corpus luteum produces levels above 1.5 [micro]g/ml or 4 ng/ml respectively.

On rare occasions, women can have a surge of preovulatory LH but not ovulate or form a fully functional corpus luteum (reviewed in Stern & McClintock, 1995). These are anovulatory cycles with atypical hormonal profiles. Therefore, when studying the association between hormones of an ovulatory menstrual cycle and any variable, it is essential to confirm the development of a functional corpus luteum from the ovulatory follicle(s). A rise in urinary pregnanediol-3-alpha-glucuronide above the assay-specific threshold indicates ovulation has occurred.

We fully recognize that, very rarely, a corpus luteum can form even when the ovulatory process is abnormal. Moreover, truly documenting ovulation itself requires visualization through laproscopy or conception, neither of which is feasible in noninvasive studies of the menstrual cycle. Thus, conservatively, what we term "the day of ovulation" should be termed "the day when the follicle became a corpus luteum." With this caveat we chose the former for the sake of brevity.

Menstrual Cycle Days

To compare hormonally similar days across participants, each participant's cycle was justified three ways relative to her preovulatory LH surge and to menses onset. First, the days were numbered relative to the LH surge (LH day 0), running both backwards (e.g., LH day -1 to LH day -14) and forwards (e.g., LH day 1 to LH day 14). Second, menses days were defined as cycle day 1, the first day of menstruation, cycle day 2, the next day, and so on until the day preceding the subject's next menstruation. Finally, premenstrual day - 1 was defined as the day before menses, running backwards until premenstrual day -4, 4 days before menses.

Menstrual Phase Definitions

Early menses is the first 3 days of menstruation (cycle days 1-3) inclusive. Menses onset was defined as the first day during menstruation that any pink or brown mucus, blood spotting, or blood was reported in vaginal secretions. Basal body temperature is typically relatively low at this time. Early menses is characterized by a hormonal profile of low levels of progesterone and estrogens and low levels of LH and follicle-stimulating hormone (FSH).

Late menses consists of cycle day 4 until the end of menses, which is defined as the first day without any pink or brown mucus, blood spotting, or blood reported in vaginal secretions. Basal body temperature is also relatively low at this time. Late menses is typically characterized by a hormonal profile of low levels of progesterone and estrogens and low levels of LH and FSH.

The follicular phase is comprised of the first day without menses through the day prior to the day of preovulatory LH surge onset (LH day--1). At this time, vaginal secretions are often opaque (white or yellow), thick, and tacky. Basal body temperature is typically low at this time. FSH causes the growth of an ovarian follicle so that the follicular phase is characterized by a hormonal profile of rising blood levels of estrogen from the developing follicle.