Evidence for a critical role of progesterone in the regulation of the midcycle gonadotropin surge and ovulation.

Serum concentrations of progesterone begin to rise just before the midcycle gonadotropin surge that leads to ovulation. To examine the role of progesterone in the regulation of these events, we evaluated the effects of a low dose (1 mg/day, orally) of the antiprogesterone RU 486 on the timing of the gonadotropin surge and ovulation in normally cycling women. The drug or a placebo was given for 5 or 15 days, starting when the dominant follicle reached 14-16 mm. RU 486 consistently delayed the timing of the midcycle gonadotropin surge and the subsequent collapse of the dominant follicle, despite rising estradiol concentrations and normal follicular development. Unexpectedly, RU 486 also delayed the emergence of the periovulatory progesterone rise. The addition of progesterone (5-10 mg/day, im, for 2 days) to a 5-day course of RU 486 after the emergence of a mature follicle readily induced LH and FSH surges and completely reversed the effects of RU 486 at midcycle. Our results suggest that RU 486 delays the midcycle gonadotropin surge and ovulation by suppressing or antagonizing an ovarian progestational signal. Progesterone may, thus, represent the ultimate ovarian signal to the estrogen-primed hypothalamic-pituitary unit to trigger the gonadotropin surge that leads to ovulation.

Serum levels of placental protein 14 do not accurately reflect histologic maturation of the endometrium.

OBJECTIVE: To determine whether serum levels of placental protein 14, a major product of the progesterone-induced secretory endometrium, accurately reflect histologic maturation of the endometrium. METHODS: Daily serum levels of placental protein 14 were compared in 50 normally cycling women with normal or delayed endometrial maturation, as assessed by histologic dating of an endometrial biopsy in the midluteal phase of the same cycle. Ten of these subjects had placental protein 14 measurements but no biopsy in an additional cycle to examine the potential effects of the biopsy on secretion of this protein. RESULTS: Serum placental protein 14 concentrations started to increase 8 days after the LH surge and peaked at similar levels on the first day of the next menses in biopsy and non-biopsy cycles. The biopsy cycles had a shorter luteal phase but a slightly faster increase in placental protein 14 concentrations. Both the integrated secretion of this protein and single measurements on the day of the biopsy or at the onset of the next menses overlapped substantially in women with different degrees of endometrial development, even when differentiation of the endometrium was severely delayed. CONCLUSION: Serum measurements of placental protein 14 do not accurately predict, and thus should not replace, histologic evaluation of the endometrium at nidation.

Effects of aging on menstrual cycle hormones and endometrial maturation.

OBJECTIVE: To investigate changes in menstrual cycle hormones and endometrial maturation that may contribute to the decline in fertility with aging. DESIGN: Prospective controlled clinical study. SETTING: Normal human volunteers in an academic research institution. SUBJECTS: Women with regular menstrual cycles. INTERVENTIONS: Thirty-two women, aged 20 to 30 or 40 to 50 years, had daily blood drawing starting on cycle day 6 to 10 and continuing until 2 days after the onset of next menses. In addition, 60 women, aged 20 to 30 or 40 to 50 years, had a total of 93 endometrial biopsies performed on day 7 to 9 after the LH surge. MAIN OUTCOME MEASURES: Serum LH, FSH, E2, inhibin, P, and placental protein 14 (PP14) levels and histologic maturation of the endometrium. RESULTS: Serum FSH levels were increased whereas inhibin concentrations were reduced in the luteal-follicular transition of women > 40 years. No other hormonal changes were seen in this population, including P and PP14 secretion. Disruption of endometrial maturation occurred at a similar frequency in both age groups. CONCLUSIONS: Follicular recruitment, but not luteal function or endometrial maturation, is disturbed in cycling women > 40 years and may contribute to the decline in fertility with aging.

Characterization of the normal progesterone and placental protein 14 responses to human chorionic gonadotropin stimulation in the luteal phase.

OBJECTIVE: To examine whether midluteal phase administration of the luteotrophic hormone hCG can result in higher and more stable serum levels than random sampling of P and placental protein 14 (PP14). DESIGN: Prospective controlled clinical study. SETTING: Normal human volunteers in an academic research environment. PARTICIPANTS: Twenty-six fertile, regularly cycling women. INTERVENTIONS: Blood samples were drawn at 0, 3, 6, 9, 12, 18, and 24 hours and then daily for the next 6 days, after a single IM injection of 5,000 IU hCG or saline given on day 5, 7, or 9 after the LH surge, as detected by rapid plasma assays. MAIN OUTCOME MEASURES: Serum P and PP14 measurements. RESULTS: Peak P and PP14 concentrations occurred at 6 hours and 5 days, respectively, after hCG stimulation on luteal phase day 9. Progesterone but not PP14 levels were significantly higher and less variable after hCG than after saline administration on this day. Progesterone responses exceeded 11.0 ng/mL (35.0 nmol/L) in all women, suggesting that this represents the cutoff limit for normal luteal function. Because PP14 responses were highly variable and inconsistent, it was not possible to determine a threshold for normal endometrial function. CONCLUSIONS: Midluteal phase administration of hCG in normal women induces consistent serum P levels > 11.0 ng/mL (35.0 nmol/L) but highly variable PP14 responses.

The antiprogestin RU486 delays the midcycle gonadotropin surge and ovulation in gonadotropin-releasing hormone-induced cycles.

OBJECTIVE: To investigate whether the antiprogestin RU486 acts primarily on the hypothalamus to delay the midcycle gonadotropin surge and thus gain insight into the site(s) of action of P in the control of ovulation. DESIGN: Prospective, crossover, single-blinded clinical study. SETTING: Outpatient clinic in an academic research environment. PATIENTS: Women with hypothalamic amenorrhea. INTERVENTIONS: RU486 or a placebo was given orally at a low dose of 1 mg/d for 5 days, starting when the dominant follicle reached 14 to 16 mm, to women with hypothalamic amenorrhea undergoing ovulation induction with GnRH pulses of unvarying frequency and dose. Blood samples and ovarian ultrasounds were obtained daily in the late follicular phase and every 3 to 4 days in the remainder of the cycle. MAIN OUTCOME MEASURES: Follicular diameter and plasma levels of LH, FSH, E2, and P. RESULTS: RU486 consistently delayed the timing of the midcycle gonadotropin surge and ovulation. Gonadotropin and steroid levels were suppressed during RU486 treatment, but follicular growth progressed normally in most patients. CONCLUSIONS: RU486 does not act primarily on the hypothalamus to delay ovulation. Rather, this compound appears to antagonize P at the pituitary level to suppress gonadotropin and steroid hormone secretion. P may thus act on the pituitary, independent of any hypothalamic effects, to regulate the timing of the midcycle gonadotropin surge and ovulation.

Midluteal phase endometrial biopsy does not accurately predict luteal function.

OBJECTIVE: To investigate whether a midluteal phase endometrial biopsy accurately predicts luteal function. DESIGN: One nonpregnant menstrual cycle was evaluated in a prospective fashion. SETTING: Outpatient Clinic of the Clinical Center of the National Institutes of Health. PARTICIPANTS: Fifty healthy, normally cycling women. INTERVENTIONS: Serum progesterone (P) was measured daily throughout the luteal phase. An endometrial biopsy was performed 7 to 9 days after the luteinizing hormone (LH) surge, as detected by rapid plasma assays, and dated histologically according to Noyes' criteria. MAIN OUTCOME MEASURE: To correlate endometrial maturation with luteal P secretion. RESULTS: Mean integrated P measurements were reduced only when the lag between histologic and chronological dating was > or = 3 days or > or = 4 days, depending on whether chronological dates were assigned prospectively from the LH surge or retrospectively from the onset of next menses, respectively. However, these lags did not consistently predict deficient luteal function because subnormal integrated P secretion was seen in only 14% of women with these delays in endometrial maturation. CONCLUSIONS: Midluteal phase endometrial biopsy provides a crude test of luteal function that does not precisely distinguish luteal insufficiency.

A prospective controlled study of luteal and endometrial abnormalities in an infertile population.

OBJECTIVE: To investigate whether luteal and endometrial abnormalities occur more frequently in an infertile population and thus contribute to infertility. DESIGN: Prospective controlled clinical study. SETTING: Outpatient clinic in an academic research institution. PARTICIPANTS: Thirty-three fertile controls and 31 infertile women without ovulatory disorders, tubal disease, or male factors. INTERVENTIONS: All women underwent an endometrial biopsy 9 days after the LH surge followed by an IM injection of 5,000 IU hCG. Blood samples were drawn immediately before hCG administration for serum P and placental protein 14 (PP14) measurements, at 6 hours after hCG stimulation for serum P concentrations, and on day 5 after hCG administration for serum PP14 levels. MAIN OUTCOME MEASURES: Histologic dating of the endometrium and serum P and PP14 measurements. RESULTS: Abnormal endometrial biopsies occurred more frequently in infertile (43%) than in fertile women (9%). Except for one case, these specimens were not associated with low hCG-stimulated P levels. Serum PP14 measurements varied widely and did not discriminate subjects with abnormal endometrial development. CONCLUSIONS: Disruption of endometrial maturation without a concomitant defect of the corpus luteum occurs more frequently in an infertile population and thus may contribute to infertility.

Delayed endometrial maturation induced by daily administration of the antiprogestin RU 486: a potential new contraceptive strategy.

OBJECTIVE: Our objective was to determine if a progesterone antagonist might interdict the development of a secretory endometrium. STUDY DESIGN: Eleven normally cycling women not at risk for pregnancy received RU 486 (1 mg/day orally) or placebo throughout one menstrual cycle in a randomized, double-blind, crossover fashion. Estradiol, progesterone, and placental protein 14 were measured every 3 days; luteinizing hormone was measured until the midcycle surge was detected. An endometrial biopsy was performed on luteal phase day 7 to 9 and interpreted with Noyes' criteria. Differences between treatment groups were analyzed by the Student t test. RESULTS: RU 486 delayed ovulation, retarded endometrial maturation, and reduced peak levels of placental protein 14 without affecting gonadal steroid production. The abnormalities in endometrial morphology and function are similar to those seen in infertile women with luteal phase defects. CONCLUSION: We hypothesize that this regimen of antiprogestin administration may prevent implantation and offer a novel strategy for fertility control.

PIP: A small clinical study has provided preliminary evidence that a daily dose of 1 mg of RU-486 produces disruption of the morphology and function of the endometrium while preserving steroidogenesis, ovulation, and timing of the cycle. Enrolled in the study were 11 nonpregnant volunteers with regular menstrual cycles who received either RU-486 or a placebo during 2 treatment cycles in a randomized, crossover fashion. RU-486 delayed the midcycle luteinizing hormone surge and prolonged the follicular phase by 1-11 days in the 9 subjects included in the final analysis but did not alter the duration of the luteal phase. The mean length of the entire cycle increased an average of 6 days in RU-486 recipients. RU-486 also caused follicular phase estradiol and luteal phase progesterone concentrations to peak later compared with the placebo group. 6 of the 10 women who ovulated during RU-486 administration had delayed endometrial morphologic characteristics; another exhibited dyssynchrony between glandular and stromal tissue. Additional evidence for the antiprogestin effect of RU-486 on the endometrium was provided by finding of significantly lower peak placental protein 14 concentrations in treated subjects. RU-486 produced no effect on premenstrual symptoms, libido, dysmenorrhea, electrolytes, liver and renal functions, and cell blood counts. The potential of a small daily dose of a progesterone antagonist such as RU-486 as a fertility control agent merits further study.

Comparative analysis of progesterone and placental protein 14 measurements in the evaluation of luteal function.

OBJECTIVE: Our purpose was to investigate the diagnostic accuracy of single or summed measurements of progesterone and placental protein 14, a progestin-dependent endometrial glycoprotein, in the evaluation of luteal function. STUDY DESIGN: Forty-five healthy women had daily blood measurements of luteinizing hormone, progesterone, and placental protein 14 during one menstrual cycle. RESULTS: Thirty-nine women had normal and six had deficient luteal function on the basis of serial progesterone determinations. Luteal insufficiency was not accurately diagnosed by single progesterone or placental protein 14 values or by integrated placental protein 14 measurements. In contrast, the condition was correctly identified in all but one cycle when the sum of progesterone on days 4 and 7 was < 49 nmol/L (15.4 ng/ml). A poor correlation was found between peak or integrated measurements of progesterone and placental protein 14. CONCLUSION: Measurement of serum progesterone, but not placental protein 14, on 2 days of the midluteal phase provides a convenient and reliable test of luteal function.