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what is menstrual cycle which hormones regulate menstrual cycle

The menstrual cycle is a monthly series of changes in the uterus and ovaries that prepares the body for a possible pregnancy. It is mainly regulated by four key hormones: FSH, LH, estrogen, and progesterone.

Quick Scoop

What is the menstrual cycle?

The menstrual cycle is a repeating sequence of physiological changes in the female reproductive system, typically lasting about 28 days, though 21–35 days is also normal.

It involves growth and release of an egg from the ovary (ovulation) and changes in the uterine lining, which thickens to support a pregnancy or sheds as menstrual bleeding (menses) if pregnancy does not occur.

You can think of it as a monthly “prepare or reset” routine: if no pregnancy happens, the built-up lining breaks down and leaves the body as blood and mucus through the vagina.

Main hormones that regulate the menstrual cycle

The cycle is controlled by a finely tuned interaction between brain and ovarian hormones.

1. Follicle-stimulating hormone (FSH)

  • Produced by the anterior pituitary gland in the brain.
  • Stimulates growth of ovarian follicles (small sacs containing immature eggs).
  • Helps a primary follicle mature into a Graafian follicle during the follicular phase.

2. Luteinizing hormone (LH)

  • Also produced by the anterior pituitary gland.
  • Gradually rises and then surges mid‑cycle, triggering ovulation (release of the egg from the ovary).
  • After ovulation, supports formation of the corpus luteum (the structure that produces progesterone).

3. Estrogen (mainly estradiol)

  • Produced by developing ovarian follicles under the influence of FSH and LH.
  • Promotes growth and thickening of the uterine lining (endometrium).
  • At certain levels, inhibits FSH and stimulates LH, helping to time the LH surge and ovulation.
  • Also responsible for secondary sexual characteristics like breast development and wider hips.

4. Progesterone

  • Secreted mainly by the corpus luteum after ovulation.
  • Prepares and maintains the endometrium for possible embryo implantation during the luteal phase.
  • High progesterone levels suppress further FSH and LH release, preventing another ovulation in the same cycle.
  • If pregnancy does not occur, progesterone levels fall, causing the uterine lining to shed and a new cycle to start.

5. Supporting hormone: GnRH (brain signal)

  • Gonadotropin‑releasing hormone (GnRH) is released by the hypothalamus in the brain.
  • Signals the pituitary gland to release FSH and LH, so it sits “above” them in the control hierarchy.

How these hormones work across the cycle

Although your question is mainly “what is it” and “which hormones,” it helps to see the phases briefly.

  1. Menstrual phase (bleeding days)
    • Estrogen and progesterone are low, causing the uterine lining to break down and shed as menstruation.
 * FSH starts to rise, recruiting new follicles in the ovary.
  1. Follicular phase (before ovulation)
    • FSH promotes follicle growth; maturing follicles produce increasing estrogen.
 * Estrogen thickens the endometrium and, when high enough, helps trigger the LH surge.
  1. Ovulatory phase (mid‑cycle)
    • A sharp LH surge causes the Graafian follicle to rupture and release the egg.
 * This is the most fertile time of the cycle.
  1. Luteal phase (after ovulation)
    • The ruptured follicle becomes the corpus luteum, which secretes progesterone (and some estrogen).
 * Progesterone stabilizes and matures the endometrium for potential implantation.

 * If there is no pregnancy, the corpus luteum breaks down, progesterone and estrogen levels fall, and menstruation begins again.

Mini FAQ style recap

  • What is the menstrual cycle?
    A roughly monthly series of changes in ovaries and uterus that prepares for pregnancy and ends with menstruation if no pregnancy occurs.
  • Which hormones regulate the menstrual cycle?
    Mainly FSH, LH, estrogen, and progesterone, with GnRH from the hypothalamus controlling FSH and LH release.
  • Typical length of the cycle?
    About 28 days on average, with a normal range of 21–35 days in many people.

Information gathered from public forums or data available on the internet and portrayed here.