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Several risks are attributed to progestins as a class-effect; however, the progestins used in hormone replacement therapy (HRT) have varying pharmacologic properties and do not induce the same side effects. Natural progesterone (P) and some of its derivatives, such as the 19-norprogesterones, do not exert any androgenic effect and, hence, have no negative effect on the lipids. On the other hand, the...
Org 31710 and Org 33628 are two highly selective progesterone receptor modulators (PRMs) with respect to their anti-progestational and anti-glucocorticoid activity. The compounds have been studied both in vitro and in vivo. Org 33628 has approximately four times stronger anti-progestational activity in vitro than does Org 31710, and in rats it is about 15 times more potent in the pregnancy interruption...
Progesterone antagonists (PAs, antiprogestins) can modulate estrogenic effects in various estrogen-dependent tissues. These modulatory effects are complex and depend on species, tissue, type of compound, dose, and duration of treatment. In non-human primates, PAs, including mifepristone, ZK 137 316 and ZK 230 211, inhibit endometrial proliferation and induce amenorrhea. When administered chronically...
The levonorgestrel intrauterine system (LNG IUS) releases 20 μg/24 h of levonorgestrel from a polymer cylinder mounted on a T-shaped frame and covered with a release rate-controlling membrane. It is approved for 5-year use. The most outstanding features of LNG IUS are its high contraceptive efficacy and reduction of menstrual blood flow. No single mode of action can account for its contraceptive efficacy...
Both progesterone receptor modulators (PRMs) as well as pure progesterone antagonists (PAs) have numerous proven and potential therapeutic applications in female health care. Mifepristone, a PRM with only marginal agonistic activity, together with a prostaglandin can terminate pregnancies of less than 9 weeks duration; mifepristone is also used in the preparation of women at later gestational stages...
Unscheduled disturbances of bleeding with long-acting progestogen-only methods continue to be a major social inconvenience, and the most common reason for premature discontinuation of use. The patterns of bleeding with different methods are now well characterised, but in spite of a substantial amount of recent research we still do not clearly understand the actual mechanisms underlying these disturbances...
Natural progesterone, which is devoid of androgenic activity, is widely used in assisted reproduction for luteal and pregnancy support. The vaginal route has become the most established way to deliver natural progesterone because it is easily administered, avoids liver first-pass metabolism, and has no systemic side-effects. The vagina has a large potential for absorption, and through the 'uterine...
Contraceptive methods for breastfeeding women should be safe for the mother and infant and should not interfere with lactation. Progestin-only methods meet these conditions and can be used from the sixth week postpartum. Because all progestins are excreted in milk, those that are insufficiently active by the oral route are preferable to avoid any possible effect on the baby. These steroids, however,...
Several progestin-only long acting contraceptives are currently available in the form of implants or injectables. Vaginal rings are another contraceptive option in the final stages of development. These steroid-containing polymer rings are placed in the vagina, providing relatively constant drug release, thus allowing for lower effective doses. Vaginal rings have the advantage of being user-controlled...
Ovarian steroids have important inter-related roles in many systems and processes required for mammalian reproduction. The female reproductive tract, ovaries, and mammary glands are all targets for both estrogen and progesterone. In addition, the actions of these hormones are intertwined in that, for example, progesterone attenuates the proliferative effect of estrogen in the uterus, whereas estrogen...
Long-term administration of progesterone antagonists (PAs) and progesterone receptor modulators (PRMs) has been proposed as a novel hormonal therapy for various hormone dependent maladies. We studied the long-term endocrine effects of mifepristone on the kinetics of estradiol (E 2 ) and its precursors, and on gonadotropin levels in five postmenopausal women treated for unresectable meningioma...
During pregnancy, the antiprogestin mifepristone will induce uterine contractions, increase the sensitivity of the myometrium to prostaglandin, and ripen the cervix. These effects indicate that mifepristone can be used for termination of pregnancy. The clinical experience has shown that mifepristone is sufficiently effective for this purpose only if combined with a suitable prostaglandin, e.g. gemeprost...
Studies were conducted to assess progesterone antagonists (PAs) and progesterone receptor modulators (PRMs) with respect to PR agonistic and antagonistic activities in vivo. These properties are not always adequately reflected in transactivation in vitro models. Studies were performed in pregnant rats, estrogen-primed rabbits (McPhail -Test), and cycling and pregnant guinea pigs. Tested compounds...
In the 1980s and 1990s, the litigious climate in the US had a catastrophic effect on sales of many major contraceptives. Although oral contraceptives escaped controversy, the intrauterine device (IUD) and Norplant(R) were two targets of damaging litigation. The IUD was withdrawn from the market in 1985. Since 1994 when the attacks began against Norplant, its US sales have dramatically declined, even...
Trimegestone (TMG) is a novel 19-norpregnane progestin under development for hormone replacement therapy and oral contraception. The objective of the current study was to characterize the potency and steroid receptor selectivity of TMG in several in vitro assays and to compare its activity to that of medroxyprogesterone acetate (MPA). TMG and MPA had a similar competitive binding affinity for human...
Estrogen replacement therapy (ERT) increases a woman's risk of developing endometrial cancer approximately 120% for each 5 years of use. ERT increases a woman's risk of developing breast cancer approximately 10% for each 5 years of use. To reduce the greatly increased endometrial cancer risk, progestins have been added to ERT (estrogen-progestin replacement therapy; EPRT) for between 5 and 15 days...
The influences of the synthetic progestin, medroxyprogesterone acetate (MPA), the progesterone receptor modulator J867, and the antagonist ZK137316 were studied in vitro on isolated endometrial epithelial cells, as well as endometrial fibroblasts. We evaluated the expression of estrogen receptor α (ER) and the progesterone receptor (PR) by RT-PCR. ER and PR were strongly expressed in the fibroblasts...
Angiogenesis, the sprouting of new blood vessels from pre-existing ones, is fundamental for human endometrial development and differentiation, which are necessary for implantation. This vascular process is supposed to be mainly mediated by the vascular endothelial growth factor (VEGF), also named vascular permeability factor (VPF). We report here the expression and modulation of VEGF and its receptors,...
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