Polycystic ovary syndrome (PCOS) and irregular periods

on Wed 5 Jul


Although some women with PCOS have regular periods, many do not and this is down to a combination of the high levels of male hormones known as androgens together with the excess insulin that is a symptom of the condition.


“Regular” periods don’t necessarily conform to a 28 day cycle; they’re still regarded as regular if they occur anywhere between 21 and 35 days. However, if your menstrual cycle is longer than 35 days or you have less than 8 cycles per year your periods are considered irregular.


There are two main reasons for seeking medical help to achieve regular cycles

  • Long gaps between periods lead to a thickening of the womb lining (endometrium) and a build-up of abnormal cells which not only lead to heavy and/or prolonged bleeding but could (rarely) lead to endometrial (womb) cancer.
  • Irregular periods imply you are not ovulating and therefore will impact on fertility


Medical treatment

  1. Hormonal birth control

Oral contraceptive pill tablets can help:

  • Correct hormonal imbalance
  • Lower testosterone levels
  • Make your periods more regular
  • Lower any risk of endometrial cancer


  1. Progestogen

If it has been a long time since you have had a period, progestogen tablets may be used to induce a period in order to clear out the lining in the womb before starting on other medications to regulate your periods.  Progestogen is usually given as an intermittent course lasting up to four months. It is not uncommon for women to experience bloating, cramps, mood swings and very heavy periods during this time.

It can also be given directly to the lining of the womb via a Mirena coil which can be effective and cause less side-effects.


  1. Metformin

This is primarily a drug issued to treat type 2 diabetes but there are some similarities between PCOS and adult onset diabetes. For example, in both conditions patients have a resistance to insulin which results in higher than usual insulin levels in the blood. This can cause an increase in the production of androgens which then adversely affects the pituitary hormones that stimulate ovulation - often leading to irregular and infertile periods.


Metformin improves the ability of insulin to lower your blood sugar which in turn can lower both insulin and androgen levels. There is good evidence of benefit with up to 90% of women starting to have regular periods/ovulate after 6 months.



It is said that losing 5% to 10% of your weight can help restore regular periods. An effective diet and exercise regime has been shown to significantly improve insulin sensitivity.


If you would like to find out more about the ideal PCOS diet please click here 


Although every effort is made to ensure that all health advice on this website is accurate and up to date it is for information purposes and should not replace a visit to your doctor or health care professional.

As the advice is general in nature rather than specific to individuals Dr Vanderpump cannot accept any liability for actions arising from its use nor can he be held responsible for the content of any pages referenced by an external link




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