Distinguish your menstrual cycle from your ovulation cycle and get to know your fertility hormones!
The Menstrual Cycle
In the days after your period (in the follicular phase of the cycle), the anterior pituitary gland in the brain starts to produce luteinizing hormone (LH) and follicle stimulating hormone (FSH). FSH and LH stimulate the immature eggs already present in the ovary to develop and grow. The eggs develop inside fluid-filled sacs called follicles. These follicles then start to produce oestrogen – the pre-ovulation hormone. It is also responsible for contributing to the growth and development of these immature eggs until one is selected for ovulation.
When ovulation occurs, the selected egg bursts out of its follicle and makes its way through the fallopian tube toward the womb. The empty follicle deflates and becomes the corpus luteum – a ‘yellow body’ which sits on the ovary and produces progesterone – the post-ovulation hormone. Ovulation marks the end of the follicular phase of the cycle and the beginning of the luteal phase. If fertilisation does not occur, the egg dies, the lining of the womb is shed as a period and the whole cycle begins again.
For some women, the fall in progesterone levels can lead to symptoms of pre-menstrual syndrome (PMS).
Luteinizing Hormone (LH)
This hormone is produced by the anterior pituitary gland in the brain. It is responsible for simulating growth of the immature eggs in the ovary. The level of LH rises to its highest the day before ovulation and this is what triggers ovulation. LH also stimulates the corpus luteum to produce progesterone.
Follicle Stimulating Hormone (FSH)
This hormone is produced by the anterior pituitary gland in the brain. It is responsible for stimulating the follicles in the ovaries to grow and develop the immature eggs. Its production is switched off by rising levels of oestrogen.
This hormone is dominant before ovulation. It helps the lining of the womb grow and helps immature eggs in the ovary develop until one is selected for ovulation. It is oestrogen that stimulates the cervix to produce mucus which indicates that ovulation is approaching. Also responsible for building healthy strong bones and good cardiovascular health.
This hormone is dominant after ovulation. It helps stabilise the lining of the womb and provide nourishment in preparation for implantation of a fertilised egg. It is also responsible for mood stabilisation and maintaining strong bones. Progesterone switches off mucus production in the cervix and if pregnancy does not occur, the progesterone levels fall and the lining of the womb becomes unstable and is shed as a period. For some women, the fall in progesterone levels can lead to symptoms of pre-menstrual syndrome (PMS). Low progesterone levels after ovulation can also be a sign of problems with ovulation and can cause pre-menstrual bleeding, brown bleeding at the end of a period and recurrent miscarriages.