Although some women with PCOS have regular periods, high levels of androgens ('male' hormones) and excess insulin can disrupt the monthly cycle of ovulation and menstruation.
If you have PCOS, your periods may be 'irregular' or stop altogether. The average menstrual cycle is 28 days with one ovulation when eggs are released, but anywhere between 21 and 35 days is considered 'normal'. An 'irregular' period cycle is defined as either:
- Eight or less menstrual cycles per year
- Menstrual cycles longer than 35 days
Some women with PCOS also experience heavier or lighter bleeding during their menstrual cycle.
Regular periods help to prevent excess thickening of the lining of the uterus (womb). Long gaps between periods can lead to abnormal cells building up inside the womb. It is important you have at least four cycles per year to avoid a build up that may include abnormal cells.
Your doctor can prescribe hormonal contraception to help regulate your menstrual periods. The medication can also reduce menstrual cramps, acne and excess hair growth. These medications include:
- A low–dose oral contraceptive pill ('the pill')
- Progesterone which stimulates the uterus and induces bleeding
- Hormonal implants
- Vaginal contraceptive rings
- Intra-uterine devices containing progesterone
How they work
The oestrogen and progesterone in hormonal contraception act to override the body's normal hormonal control of the menstrual cycle and ovulation. The oral contraceptive pill works by "switching the ovaries off", which means that when a woman is taking the pill the production of hormones such as testosterone is greatly reduced. The pill also increases the body's production of sex hormone binding globulin (SHBG), which binds to the main androgen testosterone in the blood. This reduces the activity of testosterone and reduces the symptoms of male hormone or androgen excess.
Some oral contraceptive pills (Diane/Brenda/Juliet) also contain small amounts of anti-androgens (cyproterone acetate), which aim to block the effects of testosterone and similar hormones. However, they also have higher doses of oestrogen, which may increase insulin resistance. In general, most oral contraceptives have similar effects on androgen excess.
By allowing the regular shedding of the uterus lining (endometrium) during menstruation, the pill can reduce the risk of developing endometrial cancer.
Possible side effects
Some of the more common side effects associated with hormonal contraceptive medication include:
- mood changes
- weight gain or loss
- breast tenderness
- irregular bleeding
These side effects can differ depending on the oestrogen and progesterone content of the pill/device.
The oral contraceptive pill should not be used if you have high blood pressure, are a smoker, or have had a deep vein thrombosis (DVT) in the past.
There is some recent evidence to suggest hormonal contraception may increase insulin resistance, abnormal glucose tolerance (a sign of early diabetes) and cholesterol levels (triglycerides). Low dose preparations appear to be better (such as 20µg oestrogen pills).
However, other evidence shows no negative effects of the oral contraceptive pill on risk factors for type 2 diabetes and cardiovascular disease.
The overall combined effect of hormonal contraception on the long–term health for women with PCOS is not currently known.
Use of oral contraceptive in adolescents
Experts suggest that if an adolescent has had twelve months of irregular cycles occurring at more than 35 days or less than 21 days from their first period (menarche), the possibility of PCOS should be considered before taking the oral contraceptive pill.
If you are adolescent and already taking the pill, in order to diagnose whether you have PCOS, you will need to stop taking the pill for three months to allow a hormonal assessment. If you are sexually active, another form of contraception should be used to reduce any risk of an unplanned pregnancy.
Insulin–sensitising drugs such as metformin improve menstrual regularity and ovulation. Metformin is used to treat insulin resistance and diabetes by improving the sensitivity of insulin and by suppressing glucose production by the liver.
Metformin does not appear to be quite as effective as the oral contraceptive pill in improving menstrual regularity and reducing androgen excess. It has similar effects on reducing hair growth and a more positive effect on cholesterol levels and insulin than the oral contraceptive pill. It also assists in weight loss and prevention of weight gain and reduces the risk of diabetes in those at high risk.
Metformin has been in use for around 60 years and is a drug with few serious side effects, except for in the elderly or those with liver or kidney failure. Some women who take metformin have some temporary gastrointestinal side effects (nausea, abdominal bloating, vomiting and loss of appetite). Metformin treatment can be started at lower doses to reduce the severity of these side effects. The slow release form of metformin, taken at night, has less severe side effects than standard metformin treatment.
Actions you can take
To make a decision on the best therapy for you to help with irregular periods discuss your options with your doctor and seek the best quality health care you can. Prioritise what is most important to you and communicate this with your doctor.
Last updated 24 July 2017 — Last reviewed 05 March 2014
** Currently under review **
This web page is designed to be informative and educational. It is not intended to provide specific medical advice or replace advice from your health practitioner. The information above is based on current medical knowledge, evidence and practice as at March 2014.