Amenorrhoea - no periods

Your periods are the visible endpoint of a cyclical secretion of hormones which involves several organs in your body. The showing of your period actually represents the endpoint of this hormone cycle, although you will often be asked about the first day of your period as if it is the first day of your cycle.

The cycle actually starts in your brain, in the hypothalamus. This is situated in the middle of your brain, under the cerebral cortex, which is where much of your conscious thinking goes on. The hypothalamus is more involved with unconscious acts, emotions and functions of the body that you are not aware of.

The hypothalamus secretes a hormone called gonadotrophin releasing hormone, which stimulates the making and the release of two hormones from the pituitary gland which lies at the base of the brain, below the hypothalamus. These hormones are called luteinising hormone (LH) and follicle stimulating hormone (FSH).

The gonadotrophin releasing hormone brings about the release of the FSH which acts on the ovary to stimulate the production of several follicles (these are sacs which contain the eggs). One of these quickly becomes dominant over the other follicles and continues to develop whilst the others wither and die away. This ripening follicle produces oestrogens which have specific effects on various target organs. There is a NEGATIVE feedback mechanism to the pituitary gland, which tells it to stop producing follicle stimulating hormone as no more follicles are needed. There is also a POSITIVE feedback via the hypothalamus to get the pituitary gland to produce gonadotrophin releasing hormone and luteinising hormone.

The sudden increase of luteinising hormone causes ovulation (rupture of the ripening follicle releasing the egg). The follicle then develops into a structure called the corpus luteum which produces oestrogen and progesterone. This is the other main female hormone, sometimes blamed for PMT type symptoms.

The rising levels of oestrogen and progesterone have an inhibitory effect (or negative feedback) on gonadotrophin releasing hormone. This stops the release of luteinising hormone producing degeneration of the corpus luteum, unless pregnancy occurs. The death of the corpus luteum means that there is a fall in the oestrogen and progesterone levels, reducing the negative feedback to the hypothalamus, thus starting another cycle of production. The rapid fall in progesterone also means that the thickening of the lining of the womb which has occurred earlier in preparation for a possible pregnancy can no longer be maintained and it is shed, producing the bleeding known as your period.

This delicate balance of hormonal production can be interfered with at any point. If you have stopped your periods for any length of time, your doctor may need to examine you and to perform some blood tests to establish the levels of some of these hormones. If no serious cause can be determined, the most likely cause for your amenorrhoea (lack of periods) is that this balance between the pituitary gland, the hypothalamus and the production of hormones has been temporarily interrupted. Emotional upset is well known to cause irregularity of periods and if you consider the proximity of the hypothalamus, where much emotional activity goes on, to the pituitary gland, it might be easier to understand why the menstrual cycle can be so easily affected. If you are still concerned, do speak again with your doctor.

Further information

This article published on
01 August 2005

Next review date 8/1/2013


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