Effects of levonorgestrel on capacity of mouse oocytes for fertilization and development

Progestin exposure before gonadotropin stimulation improves embryo development after in vitro fertilization in the domestic cat

This study investigated the influence of progestin priming and ovarian quiescence on response to exogenous gonadotropin stimulation in the cat. Because a subpopulation of cats routinely ovulated spontaneously, there also was the opportunity to examine the ovary's reaction to the added impact of endogenously secreted progestagen. Queens were given 1) equine chorionic gonadotropin (eCG) plus human chorionic gonadotropin (hCG) only (control; n = 9 cats), 2) GnRH antagonist (antide) injections followed by eCG and hCG (n = 9), and 3) a progestin implant (levonorgestrel) followed by eCG and hCG (n = 9). Laparoscopy was used to assess ovarian activity and aspirate follicular oocytes that were graded on the basis of morphology. In five cats per treatment, half of the high-quality oocytes were assessed for glucose, pyruvate, and lactate metabolism as well as nuclear maturation. Remaining oocytes were inseminated in vitro, cultured, and examined at 72 h after insemination for cleavage. In the remaining four cats per treatment, all oocytes were inseminated in vitro and assessed at 72, 120, and 168 h after insemination for embryo developmental stage. Cats pretreated with progestin had more follicles and produced more embryos per donor (including at the combined morula/blastocyst stage) than controls or females treated with GnRH antagonist (P < 0.05). There were no differences among groups (P > 0.05) in oocyte carbohydrate metabolism, nuclear maturation metrics, or fertilization success, although there was a tendency toward improvements in all three (P < 0.2) in progestin-treated females. Interestingly, cats that spontaneously ovulated within 60 days of treatment onset also produced more embryos per cat than induced-ovulation counterparts (P < 0.05). Results indicate that prior exposure to exogenous progestin (via implant) or endogenous progestagen (via spontaneous ovulation) improves ovarian responsiveness to gonadotropins in the cat through a mechanism that is independent of the induction of ovarian quiescence.

Priming with progestin, but not GnRH antagonist, induces a consistent endocrine response to exogenous gonadotropins in induced and spontaneously ovulating cats

Ovarian sensitivity to exogenous gonadotropin stimulation (equine chorionic gonadotropin [eCG] and human chorionic gonadotropin [hCG]) following pre-treatment with a progestin (levonorgestrel) versus GnRH antagonist (antide) was studied in cats known to be induced versus spontaneous ovulators. Queens were assigned to one of three treatments: (1) levonorgestrel implants+eCG/hCG (n=7 cats); (2) antide injections+eCG/hCG (n=7) or (3) eCG/hCG alone (control; n=7). Hormonal metabolites were assessed in fecal samples collected daily for 60 days before and during the 37 days inhibitory pre-treatment and for more than 60 days after eCG/hCG. Fecal metabolites of estradiol and progesterone were measured by radioimmunoassay. Females that maintained baseline progesterone were considered induced ovulators, whereas cats that exhibited a luteal phase before inhibition treatment were classified as spontaneous ovulators. Based on fecal hormone profiles, levonorgestrel thoroughly inhibited ovarian activity, whereas antide synchronized follicular phases but did not induce complete ovarian down-regulation. Both treatments prevented ovulation in spontaneous ovulators, but neither caused regression of existing corpora lutea (CL). Levonorgestrel, but not antide, pre-treatment resulted in a quiescent ovary at the time of eCG injection, yet endocrine responses to eCG/hCG were not different among treatments. Interestingly, spontaneously ovulating females exhibited a prolonged estradiol response to gonadotropin stimulation compared to induced ovulators, and this prolonged estradiol surge was replicated by levonorgestrel pre-treatment. Thus, the progestin levonorgestrel effectively suppresses follicular and luteal activity in the cat, resulting in a more consistent response to gonadotropin stimulation, even in females prone to spontaneous ovulation.

Levonorgestrel hormone releasing intrauterine system (Mirena) as a contraceptive in egg donors: case report

We report the safe use of levonorgestrel hormone releasing intra uterine system (Mirena) as a contraceptive in egg donors during a treatment cycle. In the first case report, a 29-year-old egg donor using the Mirena coil for contraception and two egg recipients, aged 41 years and 32 years respectively underwent standard IVF treatment, oocyte retrieval in the egg donor and in vitro fertilization followed by embryo transfer in the recipient. The outcome of IVF cycle using donor eggs was satisfactory with successful pregnancy in the egg recipient. The second case involved a 34-year-old egg donor using the Mirena coil and a 44-year-old recipient. Our findings suggest that egg donors can safely use the (Mirena) as a contraceptive device during treatment, without compromising follicular development and oocyte quality.

Toxicology of progestogens of implantable contraceptives for women

There are currently four progestogens used in implantable contraceptives marketed or tested in clinical trials: levonorgestrel in Norplant and Jadelle, etonogestrel (3-keto-desogestrel) in Implanon, nestorone in Elcometrine, and nomegestrol acetate in Uniplant and Surplant. Each progestogen was evaluated for hormonal activity and for safety in a wide variety of tests in vitro and in animals prior to their use in women. All four progestogens underwent pre-clinical testing that generally followed the format for animal testing of steroidal contraceptives published by the World Health Organization and the US Food and Drug Administration (FDA). Most of the progestogens have been tested for genotoxicity in bacterial and mammalian cultured cells and in rodents. All were tested for toxicity in short- and long-term toxicology studies in rodents and dogs or monkeys, and all were tested for their effects on reproduction and fetal development. In most cases, the progestogens were tested for carcinogenicity in two rodent species, rats and mice. Early clinical trials in small numbers of women provided additional safety data prior to the exposure of large numbers of women in Phase 3 clinical trials. The published data and data submitted to the FDA demonstrate that the implantable progestogens have no significant or unusual toxicities and have a similar safety profile to the progestogens found in the approved oral contraceptives.

Inhibition of gonadotropin surge by a brief mid-cycle regimen of ethinyl estradiol and norethindrone: possible role in in vitro fertilization

Various methods to prevent premature luteinizing hormone (LH) surge and improve cycle control during hyperstimulation for in vitro fertilization (IVF) are standard of care. The purpose of the present study was to determine the influence of a 5-day regimen of ethinyl estradiol (EE) and norethindrone (NET) on folliculogenesis, gonadotropin surge, and ovulation. In a prospective randomized and comparative study, ten patients were assigned to two groups. A combination of 50 micrograms of EE and 1 mg of NET was used in groups I and II from days 6 through 10, and days 8 through 12, respectively. Blood samples and transvaginal ultrasound imaging were carried out throughout a 28-day cycle. Follicular diameter, plasma levels of LH, follicle-stimulating hormone (FSH), estradiol and progesterone, and endometrial thickness were determined. No LH surge or ovulation was detected in any patient studied. Peak estradiol concentrations were not significantly different between the groups (152.04 +/- 107.1 pg/ml vs 162.1 +/- 56.1 pg/ml [mean +/- SD] for groups I and II, respectively). No differences were noted between the groups for serum concentrations of FSH (range: 2-9 mIU/ml) or LH (range: 2-10 mIU/ml) for any given cycle day. Mean follicular diameters were not different between groups I and II (20.5 +/- 8.1 mm2 vs 20.6 +/- 14.2 mm2). Ultrasound assessment of mid-cycle follicular growth revealed diameters ranging from 18.5 mm2 to 34.0 mm2. Endometrial thickness ranged from 8 to 10 mm. There was no evidence of ovulation on ultrasound examination and either persistence or gradual resolution of follicles through the luteal phase. Peak serum concentrations at mid-luteal phase were < or = 2 ng/ml. In this pilot study, the combination of EE and NET restricted to a 5-day course beginning on day 6 or 8 permitted folliculogenesis but effectively inhibited midcycle LH surge and ovulation. Such regimens may have a role in IVF cycles for prevention of premature LH surges, especially as stimulation regimens evolve toward decreased gonadotropin use for stimulation and strict FSH preparations with the potential need for less complete pituitary suppression.

Levonorgestrel as a postcoital contraceptive

Time-release pellets of levonorgestrel (LNG), the progestogenic hormone contained in the contraceptive system Norplant, were implanted subdermally in mice, after the animals had mated and ovulated but before uterine implantation of embryos would have occurred, to examine whether the hormone could reduce the number of embryos that subsequently implanted and, if so, when it had to be administered in the postcoital period to achieve that effect. Hybrid female mice (C57BL x CBA) were paired with breeder males (CD-1) and LNG pellets were implanted on day 0, the day on which copulation plugs were found, or on day 2 or day 3 in the postcoital period. Mice in some groups were sacrificed on day 14 of the gestation period, and numbers of fetuses and/or resorption sites were counted, while mice in other groups were allowed to go to term. When LNG pellets were implanted subdermally on day 0 of the postcoital period, pellets designed to release 1.5 mg of hormone in 21 days failed to exhibit a contraceptive effect, but pellets designed to release 5 mg of hormone in 90 days were totally effective in preventing uterine implantation of embryos. Although the 5 mg pellets did not prevent embryos from implanting in all cases when administered on day 2, they prevented pregnancies from going to term by causing resorption of those embryos that did implant. When the pellets were implanted as late as day 3 in the postcoital period, uterine implantation of embryos occurred and fetuses were carried to term. Results of the study indicate that subdermal implants of LNG inserted postcoitally can prevent uterine implantation of embryos in mice, and thereby prevent pregnancy, despite fertilization of oocytes having occurred, if the hormone implants are inserted before day 3 of the postcoital period.