Menstrual Cycle

The pituitary gland produces follicle stimulating hormone (FSH) and luteinizing hormone (LH). The follicle in the ovary produces estrogen and progesterone.

The menstrual cycle is usually around 28 days but it can vary in length from 24 to 35 days. It spans the first day of the period (day 1) to the day before the next period. A period can last for 3-7 days and is caused by shedding of the womb lining when a pregnancy does not occur. During the first two weeks of the cycle, called the follicular phase, follicle stimulating hormone (FSH) acts on the ovary causing a follicle (containing an egg) to develop. The follicle is a fluid filled sac, which contains the egg. During this time the egg is growing and maturing and preparing to be released at ovulation. Estrogen levels will rise as the size of the follicle/egg increases in size. At a critical point, the high level of estrogen will trigger the release of luteinizing hormone (LH), which is required for the final maturation of the egg. Ovulation occurs about 40 hours after the LH ‘surge’. Ovulation kits, which can be bought from supermarkets or pharmacies, measure the level of LH in the urine and so can roughly predict when ovulation is going to occur. There is also a slight rise in body temperature around this time and a change in the cervical mucus so that it becomes more slippery.

At ovulation, the egg is released from the nurturing follicle that it was growing in and it is wafted into the fallopian tube. The fallopian tubes run between the ovaries and the uterus. The egg starts to travel down the fallopian tube whereby if sperm are present, fertilization may occur and the developing embryo will travel down the fallopian tube to the uterus where it will try to implant. Therefore to become pregnant, the fallopian tubes need to be open and this is one of the first tests that take place when someone is having problems getting pregnant (along with tests to check that all the hormones are doing the right thing).

The two weeks after ovulation are called the luteal phase. The empty follicle is now called a corpus luteum and it produces progesterone. Progesterone acts on the lining of the womb to thicken it, increasing blood flow and creating an implantation window, which allows implantation of the embryo to occur. If an embryo implants, the woman will not have a period; instead the embryo will continue to grow and develop into a fetus. If there is no implantation during a menstrual cycle, then the woman will have a period around day 28 of the cycle and another cycle will start. The period is caused by the shedding of the womb lining, which is no longer needed to nurture a growing baby as there has been no pregnancy.

Premenstrual Tension Or Syndrome

A few days before the period is due (where there has not been a pregnancy) many women experience premenstrual tension. Symptoms can include breast tenderness, bloating, lethargy, depression, feel very emotional, backache, increased acne and irritability. For a few women, PMT can have a hugely negative impact on their lives. We are unsure what causes PMT as hormone levels are not different in women affected by PMT but it seems that some women may be more sensitive to progesterone. One theory is that serotonin levels are reduced during PMT and treatment can involve drugs that increase serotonin levels. Increasing exercise and changing diet may help PMT, such as reducing caffeine and alcohol intake. If simple measures like this fail to help, try keeping a diary of your symptoms and write down when your periods are. Your doctor can help with treatment and this may be in the form of the contraceptive pill or patch, and/or low doses of antidepressants.

Painful Or Heavy Periods

Unfortunately, pain during periods (dysmenorrhea) is normal and affects 90% of women. This pain tends to improve with age and after having children. Pain is caused by contraction of the womb to ensure the blood is expelled. Painkillers can be used and exercise can help. Some women who experience severe pain choose to use the oral contraceptive pill or an intrauterine device, which alter the hormone levels and reduce the frequency of painful periods. Painful periods can also be caused by endometriosis. Endometriosis is a condition where the womb lining is also present where it should not be, such as over the ovaries or over the lining of the pelvis. It can cause severe pain during periods, and one of the treatments for it is the contraceptive pill. If your periods are affecting your life to the point where you have to have time off work or school, or you also find sex very painful, your doctor might refer you to see a women’s health doctor (gynaecologist) for further treatment.

Some women experience unusually heavy periods (menorrhagia) and this can impact negatively on a woman’s life such that treatment is needed. ‘Flooding’ is the term used to describe the situation whereby normal sanitary protection is not sufficient and double protection and regular changing is required. If your periods are very heavy and affecting your quality of life, or even making you anaemic (low iron levels) you should see your doctor for help in treating this. There are non-hormonal tablets which help reduce blood loss by about a third (tranexamic/mefenamic acid), the contraceptive pill, the Mirena IUS (hormonal coil) and other surgical treatments. In the UK, the Mirena coil is the first choice in treating heavy periods, because it reduces blood loss in 9 out of 10 women within a few months of insertion. If you have tried these treatments already and they have not helped, your doctor may decide to refer you to a women’s health doctor (gynaecologist) for further investigation and specialist treatment. This may involve having an ultrasound of your womb and a biopsy to check that the womb lining looks normal. Benign muscly growths of the womb muscle, called fibroids, can cause heavy periods, and removal of these can help improve periods. Benign growths of the womb lining, called polyps, also cause heavy periods and these can be easily removed using a small camera passed through the vagina into the womb, whilst you are awake or under an anaesthetic. The womb lining can also be destroyed on purpose to reduce periods, but this only suitable once you have completed your family. As a last resort, you may be offered a hysterectomy (removal of the womb).