The menstrual cycle is the controlling influence on our fertility. A healthy menstrual cycle is instrumental in trying to conceive. It has been said that the monthly cycle IS fertility. The menstrual cycle can tell us a lot about what is happening in the body, if your circulation is adequate, if hormones are balanced, if you are actually ovulating, and much more.
28 days constitutes a normal and healthy menstrual cycle. This is what most text books will tell us. What is a normal menstrual cycle? In this post and the next, we will examine the menstrual cycle, and hopefully illustrate what a healthy cycle should look like. While everyone can not fit into one box, there is a general range that represents a healthy cycle. But let’s start from the beginning. What is a period?
Menstruation (the period) is the shedding of the endometrium lining of the uterus. This generally occurs 'monthly,' releasing blood and tissues from the uterus.
How the cycle works
The period is only one part of the amazingly complex monthly fertility cycle orchestrated by the endocrine system. The endocrine system is shown in the image.
In very simple terms, the hypothalamus produces GnRH (gonadotrophin-releasing hormones) which signals to the pituitary to produce LH (luteinizing hormones) and FSH (follicle stimulating hormone) to signal to the ovaries that it is their turn to release oestrogen and progesterone.
Phases of the menstrual cycle
Follicular phase - Phase 1
The follicular phase begins on Day 1 of your menstrual cycle. Day 1 is by definition the day your period starts. The follicular phase ends when a hormone called luteinizing hormone peaks and ovulation occurs.
In the early follicular phase, after menstrual flow has ended, the lining of the uterus is at its most thin. Levels of oestrogen and progesterone are at their lowest. At this point, the hypothalamus secretes GnRH mentioned above and this signals FSH to be 'released.' FSH initiates follicular growth in the ovary (10 - 20 follicles can develop). The developing follicles then begin to produce and release oestrogen.
The oestrogen release in the follicular phase, stimulates the proliferation (or thickening) of the uterine lining. This thickened lining is preparing for a possible pregnancy. The follicular phase typically lasts about 14 days. The luteal phase begins when the follicular phase ends.
Ovulation is followed by the luteal phase. With LH present the corpus luteum begins to secrete increasing quantities of progesterone and fairly constant levels of oestrogen.
The endometrium is now influenced by progesterone, causing it to develop to be capable of nourishing a developing embryo. If fertilisation does not occur, the decline of the hormones causes the endometrium to shed, which is dependent on hormones at all times for its health, maintenance and development. When oestrogen reaches a low enough point, the hypothalamus releases GnRH and the cycle starts over again.
Length of a healthy cycle
The usual range of a healthy cycle is between 21 and 35 days. Some women will have cycles that are very different from this; but as long as there is a pattern, regularity, a healthy body, and the follicular phase is between 12-14 days, there should be no cause for concern.
Hormone levels and ovulation create the regularity of your cycle. Failure to ovulate will affect hormonal levels, and hormonal imbalance will affect/inhibit the secretion of hormones that stimulate ovulation. In the body, this is known as a negative feedback loop.
In my next post, I will address the issues surrounding a menstrual cycle and what you can do to improve your cycle's rhythm.