The menopause
Myra Hunter, Melanie Smith in Managing Hot Flushes and Night Sweats, 2020
During the menstrual cycle, hormones are sent directly into the bloodstream from the ovaries, as well as from the adrenal glands (which are just above the kidneys). The pituitary gland at the base of the brain releases a follicle-stimulating hormone (FSH) and a luteinizing hormone (LH). FSH and LH cause the ovaries to release oestrogen and progesterone. In a feedback loop, the levels of oestrogen and progesterone in the bloodstream then regulate the amounts of FSH and LH that are produced. So during a regular menstrual cycle, this system adjusts and regulates the amounts of hormones in the body. During the first half of the menstrual cycle, FSH causes the egg (ovum) to develop and mature, and oestrogen levels rise. Ovulation (which occurs when the egg leaves the ovaries) is triggered when oestrogen reaches a certain level in the bloodstream, and this causes the pituitary to produce LH. If pregnancy does not occur, levels of oestrogen and progesterone fall, and the lining of the womb is shed. Menstruation occurs, and the whole cycle continues again.
Empirical In Vitro Fertilization for Recurrent Pregnancy Loss: Is It a Valid Concept?
Howard J.A. Carp in Recurrent Pregnancy Loss, 2020
Timing of conception in relation to ovulation may affect the spontaneous miscarriage rate. Previous studies have suggested that prolonged exposure of the gametes to the female reproductive tract may have a devastating effect on the ongoing pregnancy rate. Furthermore, aging of both spermatozoa and ova before fertilization is accompanied by a higher probability of miscarriage [38,39]. Gray et al. assessed the effect of timing of conception on the risk of miscarriage in women conceiving naturally [40]. Conception on the day of ovulation or the day preceding ovulation was considered optimal. Among patients who had miscarried in a prior pregnancy, the incidence of miscarriage was significantly higher in the index pregnancy with nonoptimally timed conceptions (22.6%), as compared with optimally timed conceptions (7.3%). This association was not observed among women with no history of pregnancy loss. Likewise, studies that assessed the optimal time of conception among women with no history of miscarriage reported no increased risk of miscarriage following conception remote from the day of ovulation [41,42]. The authors postulated that some couples are predisposed to genetic abnormalities in the gametes if fertilization does not occur at the optimal time of the cycle.
Contraception
James M. Rippe in Lifestyle Medicine, 2019
Progesterone-only pills, or “mini-pills,” contain 0.35 mg of norethindrone and are taken daily with no hormone-free days. Progestins alone act by inhibiting gonadotropin secretion, inhibiting follicular development, and suppressing ovulation in 60% of women. This results in a hypoestrogenic state less suitable for implantation. Mainly, progestins cause cervical mucous thickening and decreased tubal motility, resulting in difficulty for sperm to enter the cervix or travel through the tubes. As a result, fertilization is prevented even if ovulation does occur. This pill needs to be taken at the same time every day, preferably midday. If a pill is missed by more than three hours of usual time, a backup form of contraception needs to be used for 48 hours.7 In addition, unlike estrogen-based methods, large studies have not shown an increased risk of stroke, myocardial infarction, or VTE among users of progesterone-only methods.23 Thus, progesterone-only contraceptive methods are a reasonable choice for women with hypertension, smokers, or women with a history of VTE or at high risk for VTE.24
Cross-National Variation in Knowledge of Ovulation Timing in Sub-Saharan Africa
Published in Women's Reproductive Health, 2020
The biological process of ovulation can be understood as the release of a mature egg ready for fertilization through natural means (sexual intercourse) or through artificial methods (e.g., in vitro fertilization [IVF], artificial insemination). The phases of a normal (or typical) menstrual cycle are usually defined as the menstrual phase (days 1–5); the follicular/proliferative phase (days 6 − 13); the ovulation phase (day 14); and the luteal/secretory phase (days 15–28). Many health educators do not focus on the fertility window, but rather emphasize the menstrual calendar and calculation of the menstrual phase. The ovulation phase occurs in the middle of the menstrual cycle (day 14), which can be identified as the estrogen peak that causes the pituitary gland to release luteinizing hormone (LH). LH causes the ovary to release a mature egg ready for fertilization in the fallopian tube within 24 hours of release.
Aluminum reproductive toxicity: a summary and interpretation of scientific reports
Published in Critical Reviews in Toxicology, 2020
The development of an oocyte begins as a primordial germ cell. Early in embryonic development these cells migrate into the future site of the ovaries, undergo meiotic cell division, and multiply, resulting in primary oocytes (primordial follicle) within the ovary. Their development is arrested until puberty, when follicle stimulating hormone (FSH) produced by the pituitary gland stimulates some to begin to mature, developing through follicle stages (primary, secondary, and if fertilized tertiary (Graafian) follicles), in the process of folliculogenesis. Most die (atresia) during these stages. During the resumption of cell division, the oocyte’s nucleus (germinal vesicle) breaks down and the first polar body (that forms concomitantly during oocyte division) is extruded. Follicle cells secrete and release estrogen that feeds back to the pituitary gland to decrease FSH release and increase luteinizing hormone (LH) release. This causes the follicle to rupture, resulting in release of the egg (ovulation), that migrates into the fallopian tubes where it can be fertilized by sperm. The ruptured follicle forms a corpus luteum, a transitory endocrine organ that secretes estrogen and progesterone. The latter feeds back to the pituitary gland to decrease LH release. The fertilized oocyte forms a mature egg cell (ovum). When the oocyte and sperm chromosomes combine, it becomes a zygote, which divides as it migrates into the uterus, creating the pregnant (gravid) state.
Does Interest in Sex Peak at Mid-Cycle in Ovulatory Menstrual Cycles of Healthy, Community Dwelling Women? An 11-Month Prospective Observational Study
Published in Women's Reproductive Health, 2021
Allison B. Macbeth, Azita Goshtasebi, G. William Mercer, Jerilynn C. Prior
However, in the past it was also commonly believed that ovulation always occurred in regular, normal-length cycles (e.g., approximately 28 days). Data from a large population-based study, however, recently showed that belief to be inaccurate (Prior et al., 2015). In at least one-third of spontaneous, regular, normal-length cycles in a community-wide epidemiology study of >3000 women, ages 20–49, ovulatory disturbances were confirmed by a cycle-timed serum progesterone level below the ovulatory threshold of 9.54 nmol/L (Prior et al., 2015). Thus, the studies, both older and more recent, that alleged that women’s menstrual cycle patterns were related to interest in sex provided non-definitive evidence because they lacked hormonal confirmation of ovulation (Adams et al., 1978; Arslan et al., 2018; Jones et al., 2018a).