Hormones and The Menstrual Cycle Explained.
The menstrual cycle is a complex series of events, that all work synergistically with a primary goal to prepare the body for pregnancy. There are several hormones involve, and the cycle can be broken down in the 4 phases.
The main hormonal players.
FSH
FSH or follicle-stimulating hormone, stimulates the growth and development of ovarian follicles and ovarian oestrogen production.. Ovarian follicles contain developing eggs, so this hormone influences egg development.
LH
Luteinizing hormones stimulates ovarian oestrogen and testosterone production, and promotes final ovarian follicle egg maturation and ovulation. It also stimulates progesterone production after ovulation.
Oestrogen
Oestrogen is required for egg maturation, ovulation and promotes growth of the endometrial lining (what later becomes the tissue that is shed during a period). It is also important for bone health, and has many other functions all over the body.
Progesterone
Progesterone is made only after ovulation. Once the egg has been ovulated, the follicle becomes a secreting organ that secretes progesterone. Progesterone influences the endometrial lining with oestrogen and “prepares the body for pregnancy”. Progesterone is a calming hormone that reduces mood changes after ovulation associated with PMS and is important for healthy bones and metabolism..
Testosterone
Testosterone is a produced by the ovary and some is converted to oestrogen. Testosterone peaks just before ovulation, and this increases libido at just the right time for procreation.
Prolactin
Responsible for lactation and breast tissue development.
The menstrual cycle.
Hormone, ovarian and endometrial changes that occur throughout the cycle.
The four phases of the menstrual cycle and key hormones.
Menstruation
Starts the Cycle and Ends the Cycle.
Starts on day one of full bleed, not spotting and usually lasts 3-6 days. Hormones: All hormones are at baseline except FSH which has started to influence developing follicles in the ovary.
Follicular Phase
This phase involves follicular development, in which one follicle will become dominant, and the be the egg that is released this cycle. Hormones: Oestrogen and FSH stimulate growth of follicles, oestrogen stimulates the growth of endometrium (uterine lining).
Ovulatory Phase
The egg is released from the ovary, this is our fertile window.
Hormones: A surge in LH prelude this event, the corpus luteum is made from remnants of follicle. Endometrium is developing under oestrogen and now progesterone.
Luteal Phase
The endometrium continues developing to support implantation of embryo pending fertilisation. Corpus luteum secretes progesterone and oestrogen to support endometrial growth.
Hormones: If pregnancy is not achieved, oestrogen and progesterone withdraw and the lining of the endometrium will shed to become menstruation. FSH starts to rise to start follicular development of the next cycle.
A note on the oral contraceptive pill.
The synthetic hormones in the oral contraceptive pill act similarly to our hormones, BUT are not our hormones. The pill works to reduce follicular development, stops ovulation and thins the uterine lining to prevent implantation. When we are on the pill, we do not get the benefits of our natural hormones and we are not truly cycling.
Are you curious to learn more about your cycle? Follow along at @hollyhatton.naturopath for more cycle information, or book a 15 minute FREE discovery call here to find out how we can work together.
