Polyendocrine Metabolic Ovarian Syndrome
PMOS (formerly PCOS)
Definition
PMOS got a new name in May 2026 (it was formerly PCOS).
'P' is for polyendocrine. This is to reflect that there are multiple hormonal systems affected. There is a complex relationship between androgens such as testsosterone, hormones produced in the pitutiary gland in the brain, ovarian hormones and insulin.
'M' is for metabolic. This refelcts that this is not just a disorder of the menstrual cycle. It can have effects on metabolism, insulin sensitivity, cholesterol, weight and long-term cardiovascular risk.
'O' is for ovarian. This was retained from the previous name, as it's effect on follicular development in the ovaries and frequency of ovulation is a kew part of the syndrome. The term 'polycystic' in the old name was a misnomer as what is often seen on ultrasound is multiple follicles, not cysts.
'S' is for syndrome. This means that there are a constellation of possible symtpoms and effects from PMOS. There is variation between in how PMOS affects them.
Diagnosis and symptoms
We use the Rotterdam criteria to diagnose PMOS.
You need 2 out of 3 of the following:
1. Irregular periods - this means a cycle length that is less than 21 days (less common) or more than 35 days (more common). There is often variation from month to month in how long the cycle is.
There is considerable variation among women with PMOS in how irregular the cycles are. One woman will have a long cycle but still have a relatively regular period e.g. she might vary between 38 and 42 days between periods, while another woman will only have 1 or 2 periods a year.
2. High androgen levels - this can mean a high Free Androgen Index on blood tests, or signs of high androgen levels i.e. acne or excess 'male pattern' hair growth - on the face or chest.
3. Excess follicles in their ovaries on an ultrasound scan. A transvaginal (internal) ultrasound scan is usually needed to get a good view of the ovaries. The ovaries will often be bigger than usual and there may be >20 follicles on one or both of the ovaries.
Note, if you have irregular cycles that meet the above criteria and high androgen levels, then you don't need to have an ultrasound to make the diagnosis if you would prefer not to.
Younger girls and women shouldn't use ultrasound scan as part of their diagnosis until 8 years after their first period as the ovaries can have the appearances of excess follicles in those years without their being PMOS, so that can lead to overdiagnosis. We can still say these young women may be 'at increased risk' of PMOS if they have signs of it, and monitor and manage them accordingly.
Management
Because PMOS is so complex and affects women differently, how we manage it can vary depending on factors such as age, whether you require contraception, whether fertility is a concern etc.​
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Combined hormonal contraceptive pills can be useful to regularise periods and certain types of pill will also lower your androgen levels, so can help with acne hirsutism. However, when you stop them, periods can go back to being irregular.
Metformin can improve insulin sensitivity, and regularise periods. This can be helpful for women who have more metabolic features or if they are trying to conceive.
Inositol is a supplement which has some evidence in PMOS.
GLP-1 agonist medications can be helpful for some women who have difficulty maintaining a healthy weight due to their PMOS, and have had negative health consequences because of that eg. high blood pressure, high cholesterol, diabetes. It's important to remember these are long-term medications.
Ferility treatment is needed in some women with very infrequent or absent ovulation.
Provera - In order to protect the womb lining from becoming thickened, we can induce a bleed using a short course of a progestogen medication. This is usually done if periods are less freqent than 4 times a year.
A healthy diet and regular exercise are important for everyone with PMOS because of the underlying metabolic component.