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Biomedical subjects

M C Batista

Publications and source records attributed to M C Batista.

At least 19 recordsLinked to original sources

Mutation analysis of the follicle-stimulating hormone receptor gene in girls with gonadotropin-independent precocious puberty resulting from autonomous cystic ovaries.

OBJECTIVE: To search for germline activating mutations of the FSH receptor in girls with gonadotropin-independent precocious puberty. DESIGN: Molecular studies in human tissue. SETTING: Four girls with polycystic ovaries and gonadotropin-independent isosexual precocious puberty without clinical and molecular features of McCune-Albright syndrome. INTERVENTION(S): Peripheral blood was used for DNA extraction. The alpha-subunit of the Gs gene and the entire exon 10 of FSH receptor gene were amplified by polymerase chain reaction (PCR). Gs-alpha mutations characteristic of McCune-Albright syndrome were excluded by denaturating gradient gel electrophoresis (DGGE) and allele-specific PCR. Exon 10 of the FSH receptor gene was analyzed by DGGE and direct sequencing. MAIN OUTCOME MEASURE(S): Results of DGGE and direct sequencing. RESULT(S): No germline activating mutations were detected in exon 10 of our patients. Instead, two previously described polymorphisms were found, leading to the substitution of alanine for threonine at position 307 and of serine for asparagine at position 680 of the FSH receptor molecule. CONCLUSION(S): Germline activating mutations were not found in exon 10 of the FSHR gene in any of our patients. Further studies, preferably in ovarian tissue, will be required to exclude the presence of somatic activating mutations of the FSH receptor in these patients.

Amino Acid Substitution↗

Menstrual disorders and infertility caused by inactivating mutations of the luteinizing hormone receptor gene.

OBJECTIVE: To review clinical findings, hormone levels, and DNA analyses in genetic males and females with inactivating mutations of the LH receptor gene. DESIGN: Review of reported cases. SETTING: A university hospital. PATIENT(S): Genetic males and females with inactivating mutations of the LH receptor gene. RESULT(S): The clinical presentation in genetic males ranged from female genitalia to male genitalia with micropenis caused by Leydig cell hypoplasia. Genetic females presented with amenorrhea or oligomenorrhea, enlarged cystic ovaries, and infertility. Both males and females had elevated LH levels and LH/FSH ratios. Sequencing of genomic DNA revealed homozygous or compound heterozygous deletions, nonsense mutations, or missense mutations in the LH receptor gene. CONCLUSION(S): This study of patients with inactivating mutations of the LH receptor indicates that in genetic males, the action of hCG and LH is necessary for the normal development of primary and secondary sexual characteristics. In contrast, secondary sexual characteristics develop in genetic females in the absence of LH action, but they fail to ovulate.

Female↗

Clinical features of women with resistance to luteinizing hormone.

OBJECTIVE: To review clinical and hormonal characteristics of new and published females with LH resistance. PATIENTS: Seven sisters of patients with male pseudohermaphroditism due to LH resistance. MEASUREMENTS: Clinical characteristics, hormonal levels, pelvic ultrasound and molecular studies. RESULTS: Patients had: (1) normal female external genitalia; (2) spontaneous breast and pubic hair development at ages 9-13 years; (3) menarche at 12-20 years, followed by irregular menstrual cycles (3 weeks to 15 months); (4) infertility; (5) withdrawal bleeding after progesterone administration; (6) elevated serum LH levels (10-38 IU/l, normal 0. 9-8.4) and elevated LH/FSH ratio with normal androgen levels; (7) low or normal oestradiol levels for the follicular phase; and (8) normal or small uterus and normal or increased ovary size with one or more cysts at ultrasound examination. Ovarian biopsy showed antral follicles and confirmed lack of ovulation. One homozygous mutation in exon 11 of the LH receptor gene was found in each of 4 patients: 1 nonsense (Arg554Stop) and 2 missense mutations (Glu354Lys and Ala593Pro) and 1 microdeletion (Leu-608, Val-609) were found. In 3 patients (1 family) with the same phenotypic characteristics, no mutations in the coding sequence of the LH receptor gene were found. CONCLUSIONS: We conclude that women with LH resistance have spontaneous breast development, primary or secondary amenorrhoea, infertility, elevated serum LH levels and LH/FSH ratio with normal androgen levels and normal or enlarged cystic ovaries. Therefore, in females, primary and secondary sexual characteristics develop independently of LH action. However, LH stimulation is necessary for normal ovarian steroidogenesis and ovulation.

Adolescent↗

Diagnostic value of fluorometric assays in the evaluation of precocious puberty.

To establish normative data and determine the value of fluorometric AutoDELFIA assays (Wallac Oy) in the investigation of precocious puberty, we determined serum levels of LH, FSH, testosterone, and estradiol under basal and GnRH-stimulated conditions in 277 normal subjects at various pubertal stages and in 77 patients with precocious puberty. A substantial overlap was observed in basal and GnRH-stimulated gonadotropin levels in normal individuals of both sexes with pubertal Tanner stages 1 and 2. The 95th percentile of the normal prepubertal population was the cut-off limit between prepubertal and pubertal levels. These limits were 0.6 IU/L in both sexes for basal LH, 9.6 IU/L in boys and 6.9 IU/L in girls for peak LH after GnRH stimulation, 19 ng/dL in boys for basal testosterone, and 13.6 pg/mL in girls for basal estradiol. Basal and peak LH exceeding these limits were considered positive tests for the diagnosis of gonadotropin-dependent precocious puberty. According to these criteria, the sensitivities of basal and peak LH for the latter diagnosis were 71.4% and 100% in boys, and 62.7% and 92.2% in girls. The specificity and positive predicted value were 100% in both sexes for basal and peak LH levels. The negative predicted values for basal and peak LH were 62.5% and 100% in boys, and 40.6% and 76.5% in girls. Basal and GnRH-stimulated FSH levels overlapped among the various pubertal stages in normal subjects and were, in general, not helpful in the differential diagnosis of precocious puberty. In conclusion, basal LH levels were sufficient to establish the diagnosis of gonadotropin-dependent precocious puberty in 71.4% of boys and 62.7% of girls. In the remaining patients, a GnRH stimulation test was still necessary to confirm this diagnosis. Finally, suppressed LH and FSH levels after GnRH stimulation indicate gonadotropin-independent sexual steroid production.

Adolescent↗

No evidence of the inactivating mutation (C566T) in the follicle-stimulating hormone receptor gene in Brazilian women with premature ovarian failure.

OBJECTIVE: To investigate the presence of FSH receptor gene mutations in women with premature ovarian failure (POF). DESIGN: Clinical and molecular studies. SETTING: Research laboratory in a university setting. PATIENT(S): Fifteen 46,XX women with POF and 42 normal fertile controls. INTERVENTION(S): Exon 7 was amplified and digested with BsmI to screen for the previously described inactivating mutation C566T. Exon 10 was screened for mutations by denaturing gradient gel electrophoresis and direct sequencing. MAIN OUTCOME MEASURE(S): Polymerase chain reaction followed by restriction enzyme analysis, denaturing gradient gel electrophoresis, and direct sequencing. RESULT(S): No inactivating mutations were identified in exons 7 and 10 of the FSH receptor gene in women with familial or sporadic POF. Exon 10 had two polymorphisms, G919A and G2039A, whose allelic frequencies were 46.7% and 56.6%, respectively, in women with POF. The allelic frequency of both polymorphisms was 59.5% in normal fertile controls. CONCLUSION(S): No inactivating mutations in exons 7 and 10 of the FSH receptor gene were identified in Brazilian women with POF. A high frequency of two polymorphisms that are in linkage disequilibrium was found in exon 10 of this gene.

Adolescent↗

Ovarian resistance to luteinizing hormone: a novel cause of amenorrhea and infertility.

OBJECTIVE: To report the clinical, hormonal, and histopathological features of a woman with ovarian resistance to LH. DESIGN: Clinical study. SETTING: University hospital. PATIENT(S): A woman with amenorrhea, sister of a patient with male pseudohermaphroditism due to Leydig cell hypoplasia. INTERVENTION(S): Blood drawing before and after GnRH stimulation and also after dexamethasone and hCG administration, pelvic ultrasound, and ovarian biopsy. MAIN OUTCOME MEASURE(S): Karyotype, gonadotropin and steroid measurements, follicular diameter, ovarian histology, and sequencing of the LH receptor gene. RESULT(S): Patient had normal female external genitalia, normal breast development at puberty, rare episodes of vaginal bleeding, and infertility. The karyotype was 46,XX. She had elevated serum LH levels, whereas E2 and P concentrations were in the range seen in the early follicular phase. Pelvic ultrasound revealed a slightly hypoplastic uterus and enlarged polycystic ovaries. A normal follicular reserve for age, antral follicles, and absence of corpora lutea or albicans were observed on ovarian biopsy. Exon 11 of the LH receptor gene had a normal sequence. CONCLUSION(S): In our patient with ovarian resistance to LH, FSH stimulated follicular development until the preovulatory stage, but E2 levels remained in the early follicular phase range, still sufficient for normal pubertal feminization. Apparently, LH is necessary for ovulation and corpus luteum formation.

Adult↗

Apparent mineralocorticoid excess in a Brazilian kindred: hypertension in the heterozygote state.

BACKGROUND: Apparent mineralocorticoid excess (AME) is a cause of low-renin, low-aldosterone hypertension in which cortisol acts as a mineralocorticoid. The condition reflects an inability to inactivate cortisol to cortisone due to defective activity of the type 2 isozyme of 11beta-hydroxysteroid dehydrogenase (11beta-HSD2). Homozygous mutations in 11beta-HSD2 gene in patients with AME have been described. A 7-year-old Brazilian girl had previously been found to have AME. Her father recently presented with mineralocorticoid hypertension at age 38 years. OBJECTIVE: To describe the clinical details, to perform steroid analyses and to assess the molecular basis for the hypertension in this kindred. METHODS: The 11beta-HSD2 gene was amplified from genomic DNA by the polymerase chain reaction and sequenced by direct chain-termination sequencing on an automatic DNA sequencer. The sequencing results were validated by restriction-site polymorphism. The mutant 11beta-HSD2 protein was expressed in Chinese hamster ovary polyoma cells and enzymatic activity was assessed by metabolizing cortisol in vitro. RESULTS: Sequence analysis of genomic DNA revealed a novel C1061T point mutation in exon V of the human 11beta-HSD2 gene, resulting in an amino acid substitution of alanine by valine at codon 328 of the enzyme protein (A328V). Expression studies confirmed that the mutant protein was devoid of 11beta-HSD2 activity. A HhaI restriction-site polymorphism confirmed that the proband was homozygous for the mutation whereas both parents were heterozygotes. The father of the proband had hypertension, a normal serum potassium level, suppressed plasma renin activity and plasma aldosterone level and a moderately elevated urinary cortisol: cortisone metabolite ratio. CONCLUSIONS: AME in this kindred is caused by a novel mutation in the 11beta-HSD2 gene. Detection of hypokalaemia, at least in this kindred, is an insensitive screening test for mineralocorticoid-based hypertension. In contrast to results from previously investigated kindreds, we have demonstrated that this kindred has an abnormal phenotype in the heterozygote state. Further studies are now required in order to evaluate the role of 11beta-HSD2 activity in the pathophysiology of 'essential' hypertension.

11-beta-Hydroxysteroid Dehydrogenases↗

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.

Adult↗

Serum insulin levels, 24-hour blood pressure profile, and left ventricular mass in nonobese hypertensive patients.

In essential hypertensive patients, considered to be insulin-resistant, a blunted decline in nocturnal blood pressure is associated with increased adrenergic tone and left ventricular mass. Since insulin stimulates the sympathetic system, we tested whether insulin resistance and insulinemia influence left ventricular mass and the 24-hour blood pressure profile. We studied 29 nonobese hypertensive patients with office diastolic pressure between 95 and 110 mm Hg and normal oral glucose tolerance test after a 4-month washout period. They were then assigned to M-mode echocardiographic evaluation and 24-hour ambulatory blood pressure monitoring. The glucose and insulin responses to a 75-g oral glucose load were compared with those obtained in 16 weight-matched normotensive control subjects. During the oral glucose tolerance test the hypertensive patients compared with control subjects presented higher levels of glucose at 60 minutes (138.7 +/- 30.3 versus 108.7 +/- 35.7 mg/dL; P < .05) and 90 minutes (114.0 +/- 23.8 versus 94.8 +/- 31.1 mg/dL; P < .05) and insulin at 60 minutes (287.1 +/- 259.4 versus 142.1 +/- 83.9 pmol/L; P < .05). However, peak insulin levels after glucose load did not correlate with ambulatory blood pressure values or left ventricular mass index. Left ventricular mass index showed significant correlation with mean sleeping systolic pressure (rs = 56, P < .05) and diurnal systolic pressure (rs = .37, P < .05) but not with mean diurnal or sleeping diastolic pressures. In conclusion, our results indicate that in nonobese hypertensive patients, insulin resistance does not have any influence on the 24-hour blood pressure profile or on left ventricular mass index.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

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.

Adult↗

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.

Adult↗

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.

Adult↗

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.

Adult↗

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.

Adult↗

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.

Abortion, Habitual↗

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.

Adult↗

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.

Adult↗

Daily administration of the progesterone antagonist RU 486 prevents implantation in the cycling guinea pig.

Since progesterone is required to prepare the endometrium for implantation of an embryo, a progesterone antagonist may inhibit nidation and thus prevent pregnancy. We addressed this possibility in the guinea pig, the small laboratory animal whose reproductive physiology most resembles that of women. Daily administration of the antiprogestin RU 486 (0, 1, 2, or 3 mg/kg, subcutaneously) for 9 days after mating inhibited implantation in a dose-dependent fashion. When this compound was given daily throughout the estrous cycle, cyclic vaginal changes, ovulation, and mating were suppressed in up to 17%, 28%, and 55% of animals, respectively. Two of seven mated female animals receiving RU 486, 1 mg/kg/day, had implantation sites. Nidation was completely blocked at higher doses. Thus daily antiprogestin administration prevented pregnancy in sexually active, normally cycling guinea pigs. A similar strategy using a daily antinidatory dose of an antiprogestin may offer a novel approach to human fertility control.

Animals↗