Serum concentrations of estradiol, progesterone, and levonorgestrel are not determinants of endometrial histology or abnormal bleeding in long-term Norplant implant users

Pharmacokinetics, metabolism and serum concentrations of progestins used in contraception

Many different forms of hormonal contraception are used by millions of women worldwide. These contraceptives differ in the dose and type of synthetic progestogenic compound (progestin) used, as well as the route of administration and whether or not they contain estrogenic compounds. There is an increasing awareness that different forms of contraception and different progestins have different side-effect profiles, in particular their cardiovascular effects, effects on reproductive cancers and susceptibility to infectious diseases. There is a need to develop new methods to suit different needs and with minimal risks, especially in under-resourced areas. This requires a better understanding of the pharmacokinetics, metabolism, serum and tissue concentrations of progestins used in contraception as well as the biological activities of progestins and their metabolites via steroid receptors. Here we review the current knowledge on these topics and identify the research gaps. We show that there is a paucity of research on most of these topics for most progestins. We find that major impediments to clear conclusions on these topics include a lack of standardized methodologies, comparisons between non-parallel clinical studies and variability of data on serum concentrations between and within studies. The latter is most likely due, at least in part, to differences in intrinsic characteristics of participants. The review highlights the importance of insight on these topics in order to provide the best contraceptive options to women with minimal risks.

Effects of progestin-only contraceptives on the endometrium

INTRODUCTION

The contraceptive activity of synthetic progestins is mediated through three basic mechanisms: (a) An anti-gonadotrophic action leading to the inhibition of ovulation; (b) Changes in cervical mucus characteristics that inhibit sperm penetration and (c) desynchronization of the endometrial picture necessary for implantation.

AREAS COVERED

Mechanisms involved in the progestin-induced endometrium desynchronization are individually reviewed for each of the routes of administration and, whenever possible, by individual members of the various families of synthetic progestin derivatives.

EXPERT OPINION

For contraceptive purposes, progestins are today administered through several routes: orally, as injections, subdermally and via the vagina or the uterine cavity. Given this variety of modalities, their effects may differ, depending on the route of administration, concentration reached at the level of the endometrium and the duration of use. These are characterized by inactivation of the endometrium. Progestin-only contraception provides a safe and effective control of fertility regulation, although, they are associated with the problem of endometrial break through bleeding that may lead to discontinuation. Unfortunately, in spite of a major research effort over two decades, there is not, as yet, an established long-term intervention available to manage bleeding irregularities, making mandatory a deeper understanding of the mechanisms involved is required.

Complications of Subcutaneous Contraception: A Review

Over 62 million women in the United States are of childbearing age and 60% of them use contraception. Subcutaneous contraceptives include implantable contraceptives and subcutaneous injections. Implantable contraception involves subdermal time-release of synthetic progestin, which allows for several years of continuous, highly effective contraception. Its main effects are inhibition of ovulation and thickening of the cervical mucus. Many complications have been associated with subcutaneous contraception, including menstrual disturbances, headache, weight gain, acne, dizziness, mood disturbances, nausea, lower abdominal pain, hair loss, loss of libido, pain at the implant site, neuropathy, and follicular cysts. Using standard search engines, the complications of subcutaneous contraception are reviewed. Patients should be adequately counseled on the possible complications and side effects of subcutaneous contraception to help them make an informed decision when choosing the right contraceptive to meet their needs.

Vaginal bleeding disturbances and implantable contraceptives

Implantable contraceptives allow safe and effective fertility regulation for up to 5 years. Currently available devices release low doses of progestogens. Disruption of vaginal bleeding patterns is almost inevitable, particularly during the initial months of use. Irregular and prolonged bleeding as well as amenorrhea are common. Irregular bleeding is unpopular with most women and unacceptable to some. This review describes the vaginal bleeding disturbances induced by modern implantable contraceptives and discusses the implications of these in terms of method use and discontinuations. The cause of the irregular bleeding is not fully understood, but recent evidence suggests that an increase in endometrial vascular fragility might precipitate vessel breakdown and, hence, breakthrough bleeding. This review discusses this evidence and outline the possible mechanisms underlying breakthrough bleeding associated with implantable contraceptives. In addition, therapies for bleeding disturbances are described and their efficacy reviewed.

Implantable contraception

Although levonorgestrel contraceptive implants have been available for over 15 years, innovations have only recently led to a wider choice. These new implants offer easier insertion and removal and other advantages depending on the type of progestin. Implants prevent pregnancy by several mechanisms, including inhibition of ovulation and luteal function and alteration of cervical mucus and the endometrium. The high efficacy and ease of maintenance make implants an ideal contraceptive for many women, including adolescents, a population that uses implants infrequently but reports high satisfaction. Implants are appropriate for women who are breastfeeding, who have contraindications to estrogen, or who have diseases such as diabetes, hypertension, sickle cell anemia, or an HIV infection because implants have few metabolic or hematologic effects. Long-term use has not been associated with a decrease in BMD and generally leads to increased blood levels and iron stores. Women who wish to space their pregnancies appreciate the nearly immediate onset of action with insertion and the rapid termination of all effects with removal. All types of implants lead to menstrual changes and other side effects in some women. Adverse effects that occur in implant users more than the general population include headaches and acne. Women must be thoroughly counseled regarding the potential for menstrual alteration, side effects, and sexually transmitted infections if they do not use condoms. Despite their initial high cost, implants are a cost-effective method over several years, even when discontinued before the life of the implant.

Superficial endometrial vascular fragility in Norplant users and in women with ovulatory dysfunctional uterine bleeding

The aim of this study was to develop an objective test for superficial endometrial vascular fragility at hysteroscopy, and to apply this test to women using Norplant((R)) for contraception and to women with ovulatory dysfunctional uterine bleeding (DUB). A prospective observational study was carried out in 34 Norplant users and 20 women with menorrhagia due to ovulatory DUB. Superficial endometrial vascular fragility was assessed at hysteroscopy by observing the source and extent of frank and subepithelial bleeding during controlled collapse and redistension of the uterine cavity. Superficial endometrial blood vessels were more fragile in Norplant users compared to women with DUB (chi(2) = 11.60, P = 0.02). Superficial endometrial petechiae (chi(2) = 37.9, P < 0.0001) and ecchymoses (chi(2) = 42.2, P = 0.0001) were more frequently observed in the Norplant users than in the menorrhagia group. In Norplant users, superficial endometrial vascular fragility was increased in those with frequent bleeding or spotting during the past 30 days (chi(2) = 6.15, P = 0.01), and in those who were examined during a bleeding episode (chi(2) = 5.3, P = 0.02). Fragility was increased in the menorrhagia group during the perimenstrual period (days 24 to 05; chi(2) = 12.83, P = 0.01). There was no obvious relationship between subepithelial bleeding and circulating concentrations of oestradiol and progesterone.

Single monthly administration of the anti-progestagen Org 31710 in users of the 75 microg desogestrel progestagen-only pill: effects on pituitary-ovarian activity

Endocrine and ultrasound effects were studied of an intermittent (every 28 days) oral administration of 150 mg of the anti-progestagen Org 31710 during the continued daily use of 75 microg desogestrel (DSG) for progestagen-only contraception. A randomized, double-blind, placebo-controlled two-centre study was conducted in 50 healthy volunteers. Serum luteinizing hormone (LH), follicle stimulating hormone (FSH), oestradiol and progesterone concentrations, and follicle number and size were studied, as well as endometrial thickness, which was assessed by transvaginal sonography at least twice weekly during a single medication cycle (cycle 3-5). Forty-eight women were evaluated (Org 31710, n = 25; placebo, n = 23). Seven ovulations were observed in the treated group versus none in the placebo group. LH concentrations were higher on days 9 and 11 and oestradiol concentrations lower on day 3 in the treated group, irrespective of whether ovulation occurred. No parameter could predict ovulation. Endometrial thickness was greater on cycle days 7-13 and 19 in the treated group. However, within the Org 31710 group, no significant differences were found in volunteers who did or did not ovulate. Observed differences may be attributed to a competitive effect of Org 31710 with progestagen-induced suppression of the pituitary-ovarian axis, altered oestradiol feedback mechanisms, and/or altered receptor availability.

Correlation of endocrine profiles with bleeding patterns during use of Nestorone contraceptive implants

The relationship between ovarian hormones and bleeding patterns during continuous progestin contraception was studied in 29 women who used Nestorone (NES) releasing implants. Oestradiol and progesterone were measured in blood samples taken twice a week for 6 consecutive weeks, during months 6, 12, 18 and 24 of implant use. Retrospectively, the association between hormonal concentrations and bleeding patterns was evaluated. Twenty-four short (</= 24 days), 36 normal (25-35 days), 27 long (36-90 days) and nine episodes of amenorrhoea, as well as 28 periods of prolonged bleeding, were identified. Short cycles, periods of prolonged bleeding and amenorrhoea were characterized by low oestradiol concentrations. Bleeding after a normal or long cycle regularly occurred after a rise and fall of oestradiol or oestradiol and progesterone. The duration of bleeding was directly and significantly associated with the highest concentration of oestradiol in the previous 15 days in anovulatory cycles. Luteal activity was associated with shorter duration of bleeding. Periods of prolonged bleeding were usually initiated with a drop in oestradiol and over half ended with an increase in oestradiol. It was concluded that changes in endogenous hormone have a significant influence over the bleeding pattern during use of NES implants.

The effect of mefenamic acid on controlling irregular uterine bleeding secondary to Norplant use

The aim of this double-blind, placebo-controlled study was to evaluate the effect of mefenamic acid and placebo on controlling irregular uterine bleeding secondary to Norplant use. A total of 67 Norplant users attending the Family Planning Clinic of Chulalongkorn Hospital all had irregular bleeding. These women were randomly allocated into two groups. A total 34 users received mefenamic acid, 500 mg twice a day for 5 days, and placebos were given to the other 33 in the same manner. The total days of bleeding and spotting and the percentage of women in whom bleeding was stopped were analyzed in weeks 1 and 4. The percentage of subjects in whom bleeding was stopped during week 1 after initial treatment was significantly higher in the mefenamic acid group than the placebo group (76%, 27%; p < 0.001). In the follow-up period (4 weeks after initial treatment), a bleeding-free interval of > 20 days was found in 68% of the subjects treated with mefenamic acid and 33% treated with the placebo; the mean number of bleeding/spotting days was lower with mefenamic acid treatment (11.6 and 17.2 days; p < 0.05). The difference was statistically significant. It is concluded that mefenamic acid was more effective than placebo in short-term control of irregular bleeding and spotting associated with Norplant use.