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19.3: The Ovarian Cycle, the Menstrual Cycle, and Menopause - Biology

19.3: The Ovarian Cycle, the Menstrual Cycle, and Menopause - Biology


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The Ovarian Cycle and the Menstrual Cycle

The ovarian cycle governs the preparation of endocrine tissues and release of eggs, while the menstrual cycle governs the preparation and maintenance of the uterine lining. These cycles occur concurrently and are coordinated over a 22–32 day cycle, with an average length of 28 days.

The first half of the ovarian cycle is the follicular phase shown in Figure 1. Slowly rising levels of FSH and LH cause the growth of follicles on the surface of the ovary. This process prepares the egg for ovulation. As the follicles grow, they begin releasing estrogens and a low level of progesterone. Progesterone maintains the endometrium to help ensure pregnancy. The trip through the fallopian tube takes about seven days. At this stage of development, called the morula, there are 30-60 cells. If pregnancy implantation does not occur, the lining is sloughed off. After about five days, estrogen levels rise and the menstrual cycle enters the proliferative phase. The endometrium begins to regrow, replacing the blood vessels and glands that deteriorated during the end of the last cycle.

Practice Question

Which of the following statements about hormone regulation of the female reproductive cycle is false?

  1. LH and FSH are produced in the pituitary, and estradiol and progesterone are produced in the ovaries.
  2. Estradiol and progesterone secreted from the corpus luteum cause the endometrium to thicken.
  3. Both progesterone and estradiol are produced by the follicles.
  4. Secretion of GnRH by the hypothalamus is inhibited by low levels of estradiol but stimulated by high levels of estradiol.

[reveal-answer q=”87184″]Show Answer[/reveal-answer]
[hidden-answer a=”87184″]Statement c is false.[/hidden-answer]

Just prior to the middle of the cycle (approximately day 14), the high level of estrogen causes FSH and especially LH to rise rapidly, then fall. The spike in LH causes ovulation: the most mature follicle, like that shown in Figure 2, ruptures and releases its egg. The follicles that did not rupture degenerate and their eggs are lost. The level of estrogen decreases when the extra follicles degenerate.

Following ovulation, the ovarian cycle enters its luteal phase, illustrated in Figure 1 and the menstrual cycle enters its secretory phase, both of which run from about day 15 to 28. The luteal and secretory phases refer to changes in the ruptured follicle. The cells in the follicle undergo physical changes and produce a structure called a corpus luteum. The corpus luteum produces estrogen and progesterone. The progesterone facilitates the regrowth of the uterine lining and inhibits the release of further FSH and LH. The uterus is being prepared to accept a fertilized egg, should it occur during this cycle. The inhibition of FSH and LH prevents any further eggs and follicles from developing, while the progesterone is elevated. The level of estrogen produced by the corpus luteum increases to a steady level for the next few days.

If no fertilized egg is implanted into the uterus, the corpus luteum degenerates and the levels of estrogen and progesterone decrease. The endometrium begins to degenerate as the progesterone levels drop, initiating the next menstrual cycle. The decrease in progesterone also allows the hypothalamus to send GnRH to the anterior pituitary, releasing FSH and LH and starting the cycles again. Figure 3 visually compares the ovarian and uterine cycles as well as the commensurate hormone levels.

Practice Question

Which of the following statements about the menstrual cycle is false?

  1. Progesterone levels rise during the luteal phase of the ovarian cycle and the secretory phase of the uterine cycle.
  2. Menstruation occurs just after LH and FSH levels peak.
  3. Menstruation occurs after progesterone levels drop.
  4. Estrogen levels rise before ovulation, while progesterone levels rise after.

[reveal-answer q=”94688″]Show Answer[/reveal-answer]
[hidden-answer a=”94688″]Statement b is false.[/hidden-answer]

Menopause

As women approach their mid-40s to mid-50s, their ovaries begin to lose their sensitivity to FSH and LH. Menstrual periods become less frequent and finally cease; this is menopause. There are still eggs and potential follicles on the ovaries, but without the stimulation of FSH and LH, they will not produce a viable egg to be released. The outcome of this is the inability to have children.

The side effects of menopause include hot flashes, heavy sweating (especially at night), headaches, some hair loss, muscle pain, vaginal dryness, insomnia, depression, weight gain, and mood swings. Estrogen is involved in calcium metabolism and, without it, blood levels of calcium decrease. To replenish the blood, calcium is lost from bone which may decrease the bone density and lead to osteoporosis. Supplementation of estrogen in the form of hormone replacement therapy (HRT) can prevent bone loss, but the therapy can have negative side effects. While HRT is thought to give some protection from colon cancer, osteoporosis, heart disease, macular degeneration, and possibly depression, its negative side effects include increased risk of: stroke or heart attack, blood clots, breast cancer, ovarian cancer, endometrial cancer, gall bladder disease, and possibly dementia.


24.4. Hormonal Control of Human Reproduction

The human male and female reproductive cycles are controlled by the interaction of hormones from the hypothalamus and anterior pituitary with hormones from reproductive tissues and organs. In both sexes, the hypothalamus monitors and causes the release of hormones from the pituitary gland. When the reproductive hormone is required, the hypothalamus sends a gonadotropin-releasing hormone (GnRH) to the anterior pituitary. This causes the release of follicle stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary into the blood. Note that the body must reach puberty in order for the adrenals to release the hormones that must be present for GnRH to be produced. Although FSH and LH are named after their functions in female reproduction, they are produced in both sexes and play important roles in controlling reproduction. Other hormones have specific functions in the male and female reproductive systems.


Overview of the Menstrual Cycle in Humans

Figure 1 shows a general overview of the key regulatory factors in the menstrual cycle. The hypothalamus secretes gonadotropin releasing hormone (GnRH) which stimulates the anterior pituitary to secrete both follicle stimulating hormone (FSH) and luteinizing hormone (LH). FSH and LH are heterodimeric members of the glycoprotein hormone family and have an α:FSHβ and α:LHβ non-covalent structure, respectively. The α subunit is common to all glycoprotein hormone family members. The levels and timing of secretion of each gonadotropin is correlated by GnRH, feedback from sex steroid hormones, and other autocrine and paracrine factors such as inhibin and activin. The gonadotropins stimulate the ovary to produce the steroid hormones, estrogen or progesterone as well as several key autocrine, paracrine, and endocrine peptides. Similar to the pituitary, ovarian steroidogenesis is regulated by multiple factors. The ovarian steroid hormones in turn stimulate endometrial proliferation and affect many end organs. Although estrogen and progesterone have some feedback at the level of the hypothalamus, the more dynamic feedback occurs at the level of the anterior pituitary. Folliculogenesis, ovulation, luteinization, and endometrium growth and decline during the menstrual cycle depend on the above-mentioned autocrine, paracrine, and endocrine factors produced from this axis 1 .

Regulation of the menstrual cycle begins with influences at the level of the hypothalamus. The hypothalamus stimulates the anterior pituitary which stimulates the ovaries. One of the end organs for the ovarian sex hormones is the endometrium. The menstrual cycle is regulated by feed back and cross talk between these different components.


LUTEAL PHASE

This phase is usually 14 days long in most women. After ovulation, the remaining granulosa cells that are not released with the oocyte continue to enlarge, become vacuolated in appearance, and begin to accumulate a yellow pigment called lutein. The luteinized granulosa cells combine with the newly formed theca-lutein cells and surrounding stroma in the ovary to become what is known as the corpus luteum. The corpus luteum is a transient endocrine organ that predominantly secretes progesterone, and its primary function is to prepare the estrogen primed endometrium for implantation of the fertilized ovum. The basal lamina dissolves and capillaries invade into the granulosa layer of cells in response to secretion of angiogenic factors by the granulosa and thecal cells (43). Eight or nine days after ovulation, approximately around the time of expected implantation, peak vascularization is achieved. Figure 8 demonstrates a corpus luteum as seen on transvaginal ultrasound. Note the increased blood flow seen surrounding the corpus luteum as seen with Doppler evaluation. This time also corresponds to peak serum levels of progesterone and estradiol. The central cavity of the corpus luteum may also accumulate with blood and become a hemorrhagic corpus luteum. The life span of the corpus luteum depends upon continued LH support. Corpus luteum function declines by the end of the luteal phase unless human chorionic gonadotropin is produced by a pregnancy. If pregnancy does not occur, the corpus luteum undergoes luteolysis under the influence of estradiol and prostaglandins and forms a scar tissue called the corpus albicans.

Figure 8.

Corpus luteum as seen on transvaginal ultrasound. On the right image, note the Doppler flow indicating vascular flow surrounding the structure.

Estrogen levels rise and fall twice during the menstrual cycle. Estrogen levels rise during the mid-follicular phase and then drop precipitously after ovulation. This is followed by a secondary rise in estrogen levels during the mid-luteal phase with a decrease at the end of the menstrual cycle. The secondary rise in estradiol parallels the rise of serum progesterone and 17α-hydroxyprogesterone levels. Ovarian vein studies confirm that the corpus luteum is the site of steroid production during the luteal phase (44).

The mechanism by which the corpus luteum regulates steroid secretion is not completely understood. Regulation may be determined in part by LH secretory pattern and LH receptors or variations in the levels of the enzymes regulating steroid hormone production, such as 3β-HSD, CYP17, CYP19, or side chain cleavage enzyme. The number of granulosa cells formed during the follicular phase and the amount of readily available LDL cholesterol may also play a role in steroid regulation by the corpus luteum. The luteal cell population consists of at least two cell types, the large and the small cells (45). Small cells are thought to have been derived from thecal cells while the large cells from granulosa cells. The large cells are more active in steroidogenesis and are influenced by various autocrine/paracrine factors such as inhibin, relaxin, and oxytocin (46, 47).

In studies looking into the mechanisms regulating the menstrual cycle, LH was established as the primary luteotropic agent in a cohort of hypophysectomized women (48). After induction of ovulation, the amount of progesterone secreted and the length of the luteal phase is dependent on repeated LH injections. Administration of LH or HCG during the luteal phase can extend corpus luteum function for an additional two weeks (49).

The secretion of progesterone and estradiol during the luteal phase is episodic, and correlates closely with pulses of LH secretion (Fig. 9) (50). The frequency and amplitude of LH secretion during the follicular phase regulates subsequent luteal phase function and is consistent with the regulatory role of LH during the luteal phase (51). Reduced levels of FSH during the follicular phase can lead to a shortened luteal phase and the development of a smaller corpus lutea (52). Also, the life span of the corpus luteum can be reduced by continuous LH administration during the follicular or luteal phase, reduced LH concentration, decreased LH pulse frequency, or decreased LH pulse amplitude (53-55). The role of other luteotropic factors such as prolactin, oxytocin, inhibin and relaxin is still unclear (56, 57).

Figure 9.

Episodic secretion of LH (top) and progesterone (bottom) during the luteal phase of a woman.

Abbreviations: LH, luteinizing hormone: P, progesterone E2, estradiol LH + 8, LH surge plus 8 days. (From Filicori M, Butler JP, Crowley WF Jr. Neuroendocrine regulation of the corpus luteum in the human. J Clin Invest. 73:1638 1984.

The corpus luteum function begins to decline 9-11 days after ovulation. The exact mechanism of how the corpus luteum undergoes its demise is unknown. Estrogen is believed to play a role in the luteolysis of the corpus luteum (58). Estradiol injected into the ovary bearing the corpus luteum induces luteolysis while no effect is noted after estradiol injection of the contralateral ovary (56). However, the absence of estrogen receptors in human luteal cells does not support the role of endogenous estrogen in corpus luteum regression (59). Prostaglandin F2α appears to be luteolytic in nonhuman primates and in studies of women (60, 61). Prostaglandin F2α exerts its effects via the synthesis of endothelin-1, which inhibits steroidogenesis and stimulates the release of a growth factor, tumor necrosis factor alpha (TNFα), which induces cell apoptosis (62). Oxytocin and vasopressin exert their luteotropic effects via an autocrine/paracrine mechanism (63). Luteinizing hormone's ability to downregulate its own receptor may also play a role in termination of the luteal phase. Finally, Matrix metalloproteinases also appear to play a role in luteolysis (64).

Not all hormones undergo marked fluctuations during the normal menstrual cycle. Androgens, glucocorticoids, and pituitary hormones, excluding LH and FSH, undergo only minimal fluctuation (65-68). Due to extra-adrenal 21-hyroxylation of progesterone, plasma levels of deoxycorticosterone are increased during the luteal phase (69, 70).


The Ovarian Cycle and the Menstrual Cycle

The ovarian and menstrual cycles are regulated by hormones of the hypothalamus, pituitary, and ovaries (Figure 18.17). The ebb and flow of the hormones causes the ovarian and menstrual cycles to advance. The ovarian and menstrual cycles occur concurrently. The first half of the ovarian cycle is the follicular phase. Slowly rising levels of FSH cause the growth of follicles on the surface of the ovary. This process prepares the egg for ovulation. As the follicles grow, they begin releasing estrogen. The first few days of this cycle coincide with menstruation or the sloughing off of the functional layer of the endometrium in the uterus. After about five days, estrogen levels rise and the menstrual cycle enters the proliferative phase. The endometrium begins to regrow, replacing the blood vessels and glands that deteriorated during the end of the last cycle.

Which of the following statements about hormone regulation of the female reproductive cycle is false?

  1. LH and FSH are produced in the pituitary, and estrogen and progesterone are produced in the ovaries.
  2. Estradiol and progesterone secreted from the corpus luteum cause the endometrium to thicken.
  3. Both progesterone and estrogen are produced by the follicles.
  4. Secretion of GnRH by the hypothalamus is inhibited by low levels of estrogen but stimulated by high levels of estrogen.

Just prior to the middle of the cycle (approximately day 14), the high level of estrogen causes FSH and especially LH to rise rapidly then fall. The spike in LH causes the most mature follicle to rupture and release its egg. This is ovulation. The follicles that did not rupture degenerate and their eggs are lost. The level of estrogen decreases when the extra follicles degenerate.

Following ovulation, the ovarian cycle enters its luteal phase and the menstrual cycle enters its secretory phase, both of which run from about day 15 to 28. The luteal and secretory phases refer to changes in the ruptured follicle. The cells in the follicle undergo physical changes and produce a structure called a corpus luteum. The corpus luteum produces estrogen and progesterone. The progesterone facilitates the regrowth of the uterine lining and inhibits the release of further FSH and LH. The uterus is being prepared to accept a fertilized egg, should it occur during this cycle. The inhibition of FSH and LH prevents any further eggs and follicles from developing, while the progesterone is elevated. The level of estrogen produced by the corpus luteum increases to a steady level for the next few days.

If no fertilized egg is implanted into the uterus, the corpus luteum degenerates and the levels of estrogen and progesterone decrease. The endometrium begins to degenerate as the progesterone levels drop, initiating the next menstrual cycle. The decrease in progesterone also allows the hyp

Reproductive Endocrinologist
A reproductive endocrinologist is a physician who treats a variety of hormonal disorders related to reproduction and infertility in both men and women. The disorders include menstrual problems, infertility, pregnancy loss, sexual dysfunction, and menopause. Doctors may use fertility drugs, surgery, or assisted reproductive techniques (ART) in their therapy. ART involves the use of procedures to manipulate the egg or sperm to facilitate reproduction, such as in vitro fertilization.
Reproductive endocrinologists undergo extensive medical training, first in a four-year residency in obstetrics and gynecology, then in a three-year fellowship in reproductive endocrinology. To be board certified in this area, the physician must pass written and oral exams in both areas.


Interpreting Your FSH Levels: What FSH Test Result is Normal for You?

About 15 years ago, CHR's research established reference ranges for AMH and FSH levels by age. Before this development, IVF centers had been using universal “normal” ranges for AMH and FSH for everyone regardless of age. This practice hindered proper diagnosis of DOR, particularly in younger women, because the level of each of these hormones means something different depending on a woman’s age. For example, a completely normal level of FSH for a woman of 42 suggests premature ovarian aging (POA) if found in a 30-year-old. To really assess a woman's ovarian reserve and her IVF pregnancy chances, we need to look at age-specific levels. The chart below demonstrates the normal levels by age among CHR's patients. You can learn more about IVF after 40. It is also important to remember that hormonal birth control affects test results because it suppresses FSH.

FSH Level Chart by Age

As the table demonstrates, normal levels of FSH go from below 7.0 mIU/mL for someone younger than 33 to over 8.5 mIU/mL for a woman over 41. This chart is an important tool that we use to create tailored fertility treatment plans for our patients.

Baseline FSH and AMH Levels by Age

AgeFSH (On Day 3 of the Menstrual Cycle)AMH (Any Day of the Menstrual Cycle)
< 33 Years< 7.0 mlU/mL= 2.1 ng/mL
33-37 Years< 7.9 mIU/mL= 1.7 ng/mL
38-40 Years< 8.4 mIU/mL= 1.1 ng/mL
= 41+ Years< 8.5 mIU/mL= 0.5 ng/mL

Normal FSH levels by age, measured on day 3 of the menstrual cycle. The normal level of this hormone naturally increases as a woman gets older.

CHR developed and uses an age-based AMH and FSH levels chart, which is more accurate at predicting pregnancy chances.

Many fertility centers, unfortunately, still use universal cut-off values for all ages. This can mean that a fertility healthcare provider may give a younger woman with POA and higher FSH for her age (but within normal range based on a universal “normal” value) an inappropriate fertility treatment or misdiagnose her with “unexplained infertility.”

When a patient has high follicle stimulating hormone, some of these fertility centers also refuse to provide treatment, irrespective of patient age and other factors. Or centers may push women to egg donation (prematurely, in our opinion). This approach may ensure higher pregnancy success rates at such centers (because they are rejecting women with lower chances of pregnancy). But it leaves women with elevated FSH (and/or low AMH) ) abandoned, without access to fertility treatment with their own eggs that can be quite successful if done correctly.

CHR does not use such arbitrary cut-off values. We look at follicle stimulating hormone range in the context of a woman’s age and other factors. This way, our physicians are able to individualize fertility treatments for each woman’s level of ovarian function. We also know that with high FSH time is of the essence. We stayed open during COVID-19 closures to ensure that women could immediately initiate fertility treatment in these cases. This is why we have so many patients with stories of successful pregnancy with their own eggs with treatments like tailored in vitro fertilization!

FSH is Not a Single Best Measure of Fertility

What makes the “universal FSH cut-off” approach even more problematic is the fact that the most up-to-date medical literature suggests that follicle stimulating hormone is not as specific as it was once thought. A number of papers published by CHR's physicians (such as this one) suggest that AMH is essential in assessing ovarian reserve and pregnancy chances with IVF. 1 This makes sense because AMH level reflects the smaller follicles, which represent a majority of a woman's ovarian reserve. Given this, IVF treatment decisions based on follicle stimulating hormone alone appear outdated.

While tests to check levels of FSH and AMH are important in assessing ovarian reserve, both have limitations. Neither result can, indeed, categorically determine whether a woman can or cannot conceive, unless she has very high levels of follicle stimulating hormone. Therefore, placing too much emphasis on the levels of these hormones can be misleading. It can also be harmful, as some physicians make patients wait for lower follicle stimulating hormone levels to magically appear in the next blood test before starting an IVF cycle--a practice that wastes precious time and makes no physiological sense.


Ovarian Cycle Vs Menstrual Cycle

Ovarian cycle occurs in the ovaries whereas menstrual cycle occurs in the uterus. Human Physiology is a free online course on Janux that is open to anyone.

The Ovarian Cycle Youtube

Winter in women living in a continental climate at temperate latitudes.

Ovarian cycle vs menstrual cycle. The ovarian cycle is the series of changes that occur in the ovary during the menstrual cycle that cause maturation of a follicle ovulation and development of the corpus luteum. The lining of the uterus builds up. This series of hormone-driven events is called the menstrual cycle.

The ovarian cycle governs the preparation of endocrine tissues and release of eggs while the menstrual cycle governs the preparation and maintenance of the uterine lining. Menstrual cycle length may be an accurate predictor of ovarian aging due to its association with ovarian reserve test values and fecundability rates according to a systemic review published in. This cycle consists of menstrual phase proliferative phase and the secretory phase.

Learn more at httpjanuxoueduCreated by the University of Oklahoma Janux is. During the ovarian cycle several events occur such as hormone release follicle development and ovulation. The cyclic changes in females which take place in a span of about 28 days in the ovary vagina endometrium under the influence of the hormones FSH LH estrogen progesterone is known as a female reproductive cycle or the menstrual cycle.

They affect people who havent been through the menopause and are very common. A description of the ovarian and uterine cycles and how they line up with each other including the hormones that regulate them. It is also called the uterine cyclewhat happens in the uterus.

The menstrual cycle is a series of regular natural changes in the body. The ovarian cycle includes the development of the follicle the secretion of hormones by the follicle ovulation and the formation of the corpus luteum. On the other hand during the menstrual cycle the growth of the endometrial tissue blood supply to the tissue and the cut off when implantation does not occur and the shed of the developed tissues occur.

During each menstrual cycle an egg develops and is released from the ovaries. It is a cycle of reproductive physiology in females. The goal was to track your period for several months and see if it aligned with a new moon or a full moon which were interpreted to mean different things.

Ovarian activity is greater in summer vs. 2010 Sinauer Associates and. Each month a menstruating persons ovaries release an egg which travels down the fallopian tubes into the womb uterus.

Ovarian cycle Menstrual cycle It is a series of cyclic changes occurring in the reproductive tract of female with the periodicity of 28 days It is also known as menstrual cycle also known as endometrial cycle. The ovarian cycle describes changes that occur in the follicles of the ovary whereas the uterine cycle describes changes in the endometrial lining of the uterus. Sadava et al Life.

Each egg forms inside the ovary in a structure known as a follicle. The monthly menstrual cycle refers to the periodic series of changes that prepare the female body for the implantation of an embryo. Ovarian cycle is the cycle that happens with the ovaries.

The menstrual cycle has two main phases. Menstrual cycle is driven by the hormones from the ovarian cycle. In other words the first day of the menstrual cycle is the first day of your period.

It occurs in the ovary takes about 28 days and is controlled by the hormones gonadotropin-releasing hormone GnRH follicle-stimulating hormone FSH luteinizing hormone LH and estrogen. The Ovarian Cycle and the Menstrual Cycle. What is the Difference Between Ovarian Cycle and Menstrual Cycle.

The Science of Biology Ninth Edition published by Sinauer Associates. Menstrual cycles are influenced by sunshine. The length of a menstrual cycle is determined by the number of days from the first day of one period to the first day of the next.

Women began using lunar cycles to track menstruation- a full lunar phase is 295 days similar to a womans average cycle 3. Functional ovarian cysts are linked to the menstrual cycle. Sunshine is a factor that influences menstrual cycle.

These cycles occur concurrently and are coordinated over a 2232 day cycle with an average length of 28 days. It involves what hormones are released which differs at different times during the cycle and maturation of follicles into mature eggs and release of eggs. Blood flows in the last few days of this cycle.

It occurs in primates monkeys apes and human beings only. The Ovarian and Uterine Cycles. Some of the major differences between menstrual and oestrous cycles of organisms life are as follows.

The menstrual cycle can be described by the ovarian or uterine cycle.

Difference Between Ovarian Cycle And Menstrual Cycle Compare The Difference Between Similar Terms

Menstrual Cycle Wikipedia

The Menstrual Cycle Medcomic

Ovarian And Uterine Cycles Youtube

Menstrual Cycle Sbi4u Resource Website

The Menstrual Cycle Phases Of Your Cycle

Ovarian Cycle And Menstrual Cycle Tutorial Sophia Learning

Human Ovarian And Menstrual Cycles Diagram Of The Menstrual Cycle Download Scientific Diagram

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Ovarian Cycle Menstrual Cycle Online Biology Notes

Menstrual Cycle Ovarian Cycle Uterine Cycle Folliculogenesis Oogenesis Youtube

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The Ovarian Cycle The Menstrual Cycle And Menopause Biology For Majors Ii

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Stages of the menstrual cycle

There are two main phases of the menstrual cycle that differ, the follicular phase and the luteal phase. One can still recognize a third phase, ovulatory, characterized by the moment of ovulation.

Stages of the menstrual cycle

The duration of the menstrual cycle is around 28 days , although there are shorter cycles of 21 days and longer cycles of up to 35 days, also considered normal.

1. Follicular Phase

The first phase is called the follicular phase, which lasts approximately 14 days , varying from 9 to 23 days. This phase gets its name because the ovarian follicles are in the process of development.

Menstrual Cycle1

But, what are ovarian follicles? They are found in the ovaries and harbor immature eggs that will be released gradually over the woman’s reproductive life.

The follicular phase begins on the first day of bleeding until the egg is released, the ovulation phase. Menstruation, a period of bleeding, lasts an average of 5 days, although it can range from 3 to 7 days.

In the first days of the follicular phase, there is a large production of the hormone FSH (stimulating follicle), responsible for stimulating the ovaries to produce mature eggs.

As follicles mature, there is also high production of the hormone estrogen, resulting in thickening of the endometrium and formation of vessels, conditions that make the uterus ready to receive the fertilized egg and start pregnancy.

At the end of the phase, the main follicle continues its development and growth, secreting estrogen faster and faster, leading to a peak of estradiol around the tenth day.

In general, the main follicle continues to develop and increases in size. Estrogen secretion remains high, ensuring that the egg is in a condition to be released.

Another characteristic is the change that occurs in the mucus in the cervix, which becomes thin and watery. All of these changes consist of preparing the uterus for the possible arrival of sperm and consequent fertilization.

2. Ovulatory Phase

The ovulatory phase consists of releasing the mature egg and being able to be fertilized, which goes to the fallopian tubes or fallopian tubes and goes to the uterus. This process consists of ovulation.

Menstrual Cycle2

The day of ovulation varies depending on the length of the cycle. In many cases, it occurs on the 14th day of the cycle . However, this is not a rule and most women ovulate on different days of the cycle.

The egg has a short life span, around 24 hours. For pregnancy to occur it is necessary to have sex in the woman’s fertile period. Sperm can remain viable for up to 5 days in the female body.

For this reason, it must be considered that sexual intercourse without the use of contraceptive methods and up to 5 days before ovulation may result in pregnancy.

3. Luteal or luteal phase

The luteal phase begins with the formation of the corpus luteum, it comprises the period from ovulation to the first day of the next menstruation.

Menstrual Cycle3

The formation of the corpus luteum or yellow body occurs after ovulation due to the transformation of the walls of the ovarian follicles that become a secretory structure of the hormone progesterone, the most active in this phase.

In general, the luteal phase lasts around 12 to 16 days . The corpus luteum may deteriorate or remain active, indicating a possible pregnancy.

Progesterone promotes greater lining of the endometrium, preparing the uterus to receive the fertilized egg and fixation of the zygote.

If nesting does occur, the production of hCG (Human Chorionic Gonadotrophin), known as the pregnancy hormone, begins, keeping the corpus luteum active.

If fertilization does not occur, the corpus luteum degenerates and a new cycle begins with the onset of menstruation.


Phases of the menstrual cycle

Follicular phase

1. At the beginning of the menstrual cycle, levels of FSH rise causing stimulation of a few ovarian follicles.

2. As follicles mature they compete with each other for dominance.

3. The first follicle that becomes fully mature begins to produce large amounts of oestrogen.

4. Oestrogen inhibits the growth of the other competing follicles.

5. The single follicle that reaches full maturity during this process is referred to as the Graafian follicle (the oocyte develops within this).

6. The Graafian follicle continues to secrete increasing amounts of oestrogen.

7. Increasing amounts of circulating oestrogen results in:

  • endometrial thickening
  • thinning of the cervical mucus to allow easier passage of sperm
  • inhibition of LH production by the pituitary gland

8. As oestrogen levels rise, they eventually surpass a threshold level, at which point they conversely stimulate LH production, resulting in a spike in LH levels around day 12.

9. The high amounts of LH cause the membrane of the Graafian follicle to become thinner.

10. Within 24-48 hours of the LH surge, the follicle ruptures releasing a secondary oocyte.

11. The secondary oocyte quickly matures into an ootid and then into a mature ovum.

12. The mature ovum is then released into the peritoneal space and is taken into the fallopian tube via fimbriae (finger-like projections).

Luteal phase

13. Once ovulation has occurred LH and FSH stimulate the remaining Graafian follicle to develop into the corpus luteum.

14. The corpus luteum then begins to produce the hormone progesterone.

15. Increased levels of progesterone result in:

  • the endometrium becoming receptive to implantation of the blastocyst
  • negative feedback causing decreased LH and FSH (both needed to maintain the corpus luteum)
  • an increase in the woman’s basal body temperature

16. As the levels of FSH and LH fall, the corpus luteum degenerates.

17. Degeneration of the corpus luteum results in loss of progesterone production.

18. The subsequent falling level of progesterone triggers menstruation and the entire cycle begins again.

However, if fertilisation occurs…

19. If an ovum is fertilised it produces hCG which is similar in function to LH.

20. hCG prevents degeneration of the corpus luteum (resulting in the continued production of progesterone).

21. Continued production of progesterone prevents menstruation.

22. The placenta eventually takes over the role of the corpus luteum (from 8 weeks gestation).


How do FSH levels test menopause and fertility?

Follicle-stimulating hormone is a gonadotropin. This is a type of hormone that stimulates the gonads. The gonads are the ovaries in women and the testes in men.

Follicle-stimulating hormone (FSH) is secreted from a small gland in the brain called the anterior pituitary.

This article explores what FSH levels are and how they may be tested for in relation to menopause and fertility.

Share on Pinterest FSH levels, estrogen, and testosterone can be determined using a blood test.

In women, follicle-stimulating hormone helps to mature the ovarian follicles that release the eggs. Men’s bodies use FSH to support the growth and development of sperm.

Without the release of FSH, a woman cannot continue her reproductive cycle, as her ovaries will not release an egg.

FSH levels can be tested in both sexes to assess fertility, or to see if a woman is going through menopause.

Doctors can do a blood test to measure FSH levels. This is usually done alongside tests for other sex hormones, such as testosterone or estrogen.

Doctors often order the FSH test as part of a range of tests. There are a number of reasons to carry out the FSH test, including:

  • Menopause testing: If a woman’s menstrual cycle has become irregular or she has not had her period at all, a doctor may order the test. If FSH levels are high, it could indicate menopause.
  • Female fertility testing: If a woman is not ovulating, her FSH levels might be either high or low, depending on the cause.
  • Male fertility testing: In men, FSH stimulates the growth of sperm cells. If a man’s FSH levels are high, it can mean the testicles are not functioning properly.

In addition to testing for fertility and menopause, doctors may order an FSH test to look for a pituitary disorder, or to determine if a child is entering puberty too early or too late.

The U.S. Food and Drug Administration (FDA) have also approved a urine test that measures FSH levels. This test can be done at home. If a woman has difficulty conceiving, the test can show if she is in the early stages of menopause.

FSH levels are usually just one part of the puzzle a doctor has to work out. To gain a clearer picture, further tests are likely to be needed. Examples include tests for:

Also, when testing for fertility, a doctor may ask a woman to track her temperature, as this can rise during ovulation. Similarly, they may order imaging scans to check the fallopian tubes. If the tubes are blocked, the woman’s egg cannot travel to the uterus for implantation.

According to The North American Menopause Society, if a woman has an FSH level of 30 milli-international units per milliliter (mIU/mL) or higher, and has not had a period for one year, she has probably reached menopause.

However, if a woman has a single FSH test with this result, it does not mean she has reached menopause. She will need multiple tests to establish this.

According to Mayo Medical Laboratories, the reference values (most typical values) for FSH are:

  • Males older than age 18: 1.0-18.0 International Units Per Liter (IU/L)
  • Postmenopausal women: 16.7-113.6 IU/L
  • Follicular: 3.9-8.8 IU/L
  • Midcycle: 4.5-22.5 IU/L
  • Luteal: 1.8-5.1 IU/L

A doctor will provide a reference list for FSH testing results, so that someone can identify whether their levels are normal, low, or high. A doctor will explain the results and recommend treatments.

If a woman is in early menopause, a doctor may recommend hormone replacement therapy to reduce the associated symptoms.

The FSH test usually consists of a simple blood test. A small sample of blood is needed and the risks are minimal, so a person can return to their everyday activities afterward.

A doctor will not use the FSH test alone to determine if a woman is going through menopause, or to identify reasons for infertility.

One problem with hormone testing is that a person’s hormones fluctuate over the course of hours and days. So, a blood sample and testing it for hormones provides only a “snapshot” of their levels.

A diagnosis based on FSH levels alone might be inaccurate in the case of a woman. However, men are considered to have steadier hormone levels.

There are certain medications that can affect FSH levels. It is important for the individual to tell the doctor all the medications they are taking to prevent false readings. Examples of medicines that could increase FSH levels include:

Medicines that decrease FSH levels include:

Taking multivitamins that contain biotin or vitamin B7 may also affect the accuracy of the FSH test. Doctors usually recommend a woman refrain from taking these supplements for at least 12 hours before a test.

FSH tests can help a doctor evaluate fertility or menopause status.

For a woman, a doctor may recommend she has several blood samples drawn over the course of her menstrual cycle to see if her FSH levels are consistently high, low, or normal.

However, most women going through menopause will not require FSH testing.

If women are older than 45 the following symptoms alone are usually enough to confirm they are going through the menopause:

However, if a woman or a man is under 40 and wants to be tested for fertility concerns or early menopause, the FSH test can be an important in making a diagnosis.


Watch the video: Juniorská univerzita LF - Hormonální cyklus ženy prof. MUDr. M. Štengl,. (July 2022).


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