The menstrual cycle

For most women their periods have a fairly predictable pattern. A typical menstrual cycle lasts 28 days with day 1 of the menstrual cycle being defined as the first day of bleeding. Periods last for a few days and then most women do not experience bleeding again until the next period starts.

Menarche, that is the first ever menstrual period, typically occurs at the age of 12 but puberty can start as early as age 8. The first change of puberty is usually the development of breast buds, followed by pubic hair and finally menstruation. It is common to experience irregular cycles as periods regulate but usually the cycle will become fairly regular during teenage years.

The control of the menstrual cycle is dictated by the co-ordination of various hormones released by specialised areas of the brain and by the ovaries. The system is collectively known as the hypothalamo-pituitary-ovarian (HPO) axis. The chemical signals (hormones) from the brain in turn stimulate the development of the egg-containing follicles within the ovaries and the ovaries produce the hormones oestrogen and progesterone. If the HPO axis functions normally, ovulation occurs in the mid-cycle and if a pregnancy does not develop, the internal lining of the uterus, known as the endometrium, is shed 2 weeks later as a menstrual period.

A major part of gynaecology care is assessing and investigating when periods cause concerns, either because they are heavy, or painful, or irregular or a combination of these symptoms. By taking hormone blood tests and assessing the uterus and ovaries with ultrasound it is usually possible to determine if there is any significant disruption in the menstrual cycle and treatment options can be discussed accordingly.

This is all part of the gynaecologist's role and if you have any concerns about your periods or if you would like to know more about how the female reproductive system works, feel free to make an appointment to discuss these issues in more detail.