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Hormonal Control of Menstrual Cycle

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Menstrual Cycle

The menstrual cycle is a sequence of natural changes that take place in hormone production and in the structures of the uterus and ovaries of the female reproductive system that makes the woman’s body ready for pregnancy. 

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Hormonal Control of Menstrual Cycle

There are 4 hormones that control the menstrual cycle controlled by the interaction of hormones: luteinizing hormone, follicle-restoring hormone, and the female sex hormones estrogen and progesterone. The ovarian hormones are circulated in the blood and are then excreted in the forms of urine. The cyclic events in the ovary depend on gonadotropic hormones secreted by the anterior lobe of the pituitary gland; There are three gonadotropic hormones: luteinizing hormone (LH), follicle-stimulating hormone (FSH), and, possibly, luteotropic hormone (LTH).

The Menstrual Cycle has Three Phases:

  • Before the release of the eggs - Follicular phase

  • The egg release - Ovulatory phase

  • After the egg release - Luteal 

The follicular phase commences with the menstrual cycle, which begins with menstrual bleeding (menstruation). The levels of estrogen and progesterone are low in this phase. Due to this, it leads to the breakage of the top layers of the thickened lining of the uterus (endometrium) and shed in the form of blood. At this time, the development of several follicles in the ovaries is stimulated by the increased level of FSH follicle-stimulating hormone. Each follicle has an egg. After this, only one follicle continues to develop with the decrease in the follicle-stimulating hormone level. This follicle further leads to the production of estrogen.


The ovulatory phase commences with an increase in luteinizing hormone and FSH (follicle-stimulating hormone) levels. Luteinizing hormone vitalizes the release of the egg (ovulation), which occurs 16 to 32 hours after the surge starts. The estrogen level decreases, and progesterone increases during the surge. 


During the luteal phase, there is a decrease in luteinizing hormone and follicle-stimulating hormone levels. The follicle, which is ruptured, closes after the release of the egg and leads to a formation of a corpus luteum, which results in the production of progesterone. The estrogen level is high during most of this phase: estrogen and progesterone cause the lining of the uterus to thicken as a preparation for possible fertilization.


The corpus luteum degenerates if the egg is not fertilized, and hence the production of progesterone stops, and also the estrogen level decreases, which leads to the breakage of the top layers of the lining and are shed in the form of menstrual bleeding. 


However, if the egg is fertilized, the corpus luteum works during early pregnancy. It helps maintain the pregnancy.

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Hormonal Pills for Periods

There is a huge role of hormones in maintaining the menstruation cycle. The hormonal regulation of the menstrual cycle will determine the fertility of the women. There are types of hormonal contraception (for example, the oral contraceptive pill, IUD coil, injection) that may have an effect on your menstrual cycle. This could cause a change in your periods’ frequency or flow. 


Generally, oral contraceptive pills will help you to make your periods lighter. You may notice that the flow of your period’s changes and your periods have become while your cycle adapts to the changing hormones. After months of taking the pill, your periods should have now taken a regular routine. Some women have also said that their periods stop after taking the contraceptive pill.


Hormonal injections can also cause irregularity in your periods for a while before your body adapts to the hormones. However, some women experience heavier periods when they start getting hormonal injections, although periods usually become much lighter over time. A contraceptive implant can also give you irregular periods. 


The IUD (Mirena) coil can also affect your periods. You may experience some irregular spotting (light bleeding at an irregular time of your cycle) or bleeding if it has been fitted in the last six months. After that, many women find that their periods stop. Some also shared that their periods become much irregular or lighter. This is quite common among women. 

Hormonal Pills for Irregular Periods

Some women use medication and lifestyle modification to regularize the periods. You can use hormonal contraception for this purpose which includes:

  • a combined oral contraceptive pill (‘the pill’)

  • progesterone, which helps in stimulation of the uterus and induces bleeding

  • the hormonal implants

  • vaginal contraceptive rings

  • intrauterine devices have progesterone.

The progesterone and oestrogen in hormonal contraception interact with the body’s control of the menstrual cycle and ovulation. The oral contraceptive pill function by ‘switching off the ovaries’ means that if a woman consumes the contraceptive pill, her production of hormones such as testosterone is significantly decreased.


The oral contraceptive pill (‘the pill’) decreases the ovarian production of testosterone and other androgens. It also helps in the body’s production of sex hormone-binding globulin (SHBG). This leads to a reduction in the role of testosterone and hence reduces the symptoms of male hormone or androgen excess.


Oral contraceptives can badly affect insulin resistance and increase the risk of type 2 diabetes, especially in very obese women with PCOS. 


There are medications used for irregular periods. The most famous is Medroxyprogesterone is used to treat irregular vaginal bleeding or abnormal menstruation (periods). Medroxyprogesterone is also used to normalize the menstrual cycle in women who menstruate naturally in the past but who have not been menstruated for at least six months and are not pregnant or undergoing menopause (change of life). Medroxyprogesterone is also aids in the prevention of overgrowth of the lining of the uterus (womb) and can also reduce the risk of cancer of the uterus in patients who are consuming estrogen. It functions by restricting the growth of the lining of the uterus and hence causes the uterus to produce some hormones.

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FAQs on Hormonal Control of Menstrual Cycle

1. What is the hormonal control of the menstrual cycle?

The hormonal control of the menstrual cycle is a complex interaction between hormones from the hypothalamus (GnRH), the anterior pituitary gland (LH and FSH), and the ovaries (estrogen and progesterone). These hormones work in a feedback system to regulate the cyclical changes in the uterus and ovaries, preparing the female body for a potential pregnancy each month.

2. Which four main hormones regulate the human menstrual cycle and what are their roles?

The four main hormones are:

  • Follicle-Stimulating Hormone (FSH): Secreted by the pituitary gland, FSH stimulates the growth and maturation of ovarian follicles, each containing an egg.
  • Luteinizing Hormone (LH): Also from the pituitary gland, a sharp increase in LH (known as the LH surge) triggers ovulation—the release of a mature egg from the ovary.
  • Estrogen: Produced by the developing follicles, estrogen is responsible for rebuilding the uterine lining (endometrium) after menstruation. It also regulates the secretion of pituitary hormones.
  • Progesterone: Produced by the corpus luteum after ovulation, progesterone further prepares the endometrium for implantation and helps maintain the uterine lining during a potential pregnancy.

3. What are the different phases of the menstrual cycle and the key hormonal events in each?

The menstrual cycle is divided into four main phases based on hormonal events:

  • Menstrual Phase (Days 1-5): Low levels of estrogen and progesterone cause the breakdown of the uterine lining, leading to menstruation.
  • Follicular Phase (Days 1-13): The pituitary gland releases FSH, stimulating follicle growth. The growing follicles produce estrogen, which starts to rebuild the uterine lining.
  • Ovulatory Phase (Day 14): A surge in estrogen causes a spike in LH levels (the LH surge), which triggers the release of the mature egg from the ovary (ovulation).
  • Luteal Phase (Days 15-28): The remnant of the follicle forms the corpus luteum, which secretes high levels of progesterone. This maintains the thickened uterine lining, awaiting a fertilized egg.

4. How do the levels of pituitary and ovarian hormones fluctuate throughout a typical 28-day cycle?

Hormone levels change predictably. In the early follicular phase, FSH levels are slightly elevated. As follicles grow, estrogen levels rise steadily, peaking just before ovulation. This estrogen peak causes a massive LH surge, which triggers ovulation. After ovulation, during the luteal phase, progesterone levels rise significantly, and estrogen levels remain moderately high. If no pregnancy occurs, both progesterone and estrogen levels drop sharply, initiating menstruation.

5. How does the feedback loop between the pituitary gland and the ovaries regulate the cycle?

The regulation relies on both negative and positive feedback. For most of the cycle, estrogen and progesterone exert negative feedback on the pituitary, suppressing FSH and LH release. However, just before ovulation, the high levels of estrogen from the mature follicle switch to a positive feedback mechanism, stimulating the pituitary to release the LH surge. This switch is crucial for ovulation to occur.

6. Why is the LH surge in the mid-cycle considered a critical event for ovulation?

The LH surge is the primary trigger for ovulation. This rapid and significant increase in Luteinizing Hormone levels causes the mature Graafian follicle in the ovary to rupture and release its egg. Without this hormonal peak, the follicle would not break open, and ovulation would not occur, making pregnancy impossible for that cycle. It is the definitive event that marks the transition from the follicular to the luteal phase.

7. What happens to the corpus luteum if fertilisation does not occur, and how does this trigger menstruation?

If the egg is not fertilized, the corpus luteum begins to degenerate after about 10-12 days. As it breaks down, its production of progesterone and estrogen plummets. The sharp drop in progesterone levels removes the hormonal support for the thickened uterine lining (endometrium). This causes the blood vessels in the endometrium to constrict and the lining to break down and shed, resulting in menstruation.

8. What is the key difference between the hormonal control in the follicular phase versus the luteal phase?

The primary difference lies in the dominant hormone and its feedback effect. The follicular phase is dominated by estrogen, which initially uses negative feedback but then switches to positive feedback to trigger the LH surge. In contrast, the luteal phase is dominated by progesterone, which maintains strong negative feedback on the pituitary gland, preventing the development of new follicles and another ovulation event within the same cycle.

9. How do hormonal contraceptives, like the pill, interfere with the natural hormonal control of the menstrual cycle to prevent pregnancy?

Hormonal contraceptives contain synthetic versions of estrogen and progesterone. By providing a constant, low level of these hormones, they disrupt the natural cycle. They primarily work by exerting continuous negative feedback on the hypothalamus and pituitary gland. This suppresses the secretion of FSH and, most importantly, prevents the LH surge. Without the LH surge, ovulation does not occur, and thus pregnancy is prevented.


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