PMOS, the condition formerly called PCOS

What PMOS is

The Endocrine Society estimates that PMOS affects about one woman in eight. In many women with PMOS the ovaries do not release an egg every month, levels of androgens (hormones such as testosterone) are raised, and insulin resistance is common. The consensus that renamed the condition found the old name misleading: there is no increase in abnormal cysts on the ovary, and the word “polycystic” hid the condition's hormonal and metabolic features.

Common signs include irregular or absent periods, difficulty getting pregnant, excess hair growth, acne, weight gain and changes in mood. Having one of these signs does not mean you have PMOS, and not everyone with PMOS has all of them. There is no cure, but treatment and lifestyle changes can help. The new name is being introduced over about three years and will be used throughout the next international guideline, planned for 2028.

How it is diagnosed

Under the 2023 international guideline, PMOS is diagnosed in adults when two of three features are present: irregular or absent ovulation, raised androgens (shown by blood tests or by signs such as excess hair growth), and ovaries with many small follicles on ultrasound. In adults a raised AMH level can be used instead of the ultrasound, but it is not relied on alone. Other conditions that can cause similar symptoms are considered.

Because PMOS is also a metabolic condition, the guideline recommends assessing blood glucose and considering an oral glucose tolerance test for women with PMOS who are planning a pregnancy or fertility treatment. It notes that routine insulin blood tests add little to care.

What it can mean for fertility

PMOS can make it harder to get pregnant, usually because the ovaries do not release an egg each month, so there are fewer chances to conceive in a year. PMOS is also linked with a higher risk of some pregnancy complications, including miscarriage, diabetes in pregnancy and high blood pressure in pregnancy, which is why metabolic health is assessed before trying to conceive.

Treatment options, their limits and risks

• Lifestyle. The 2023 international guideline recommends healthy eating and regular physical activity for all women with PMOS; they improve metabolic health even without weight loss. NICE notes that for women with a BMI of 30 or more who are not ovulating, losing weight is likely to improve the chance of conceiving.
• Medicines to induce ovulation. The 2023 international guideline recommends letrozole as first-line medicine for women with PMOS who are not ovulating and have no other fertility factors. Clomifene, with or without metformin, is an alternative. These medicines can cause more than one egg to be released, which raises the chance of twins. See natural conception and ovulation induction.
• Second-line options. Low-dose gonadotrophin injections, increased gradually with ultrasound monitoring and aiming for a single follicle, with the cycle cancelled if too many develop; or laparoscopic ovarian surgery (“ovarian drilling”), which carries the usual risks of an operation.
• IVF. Considered when ovulation treatments have not worked or when there are other fertility factors. Ovaries with many follicles can over-respond to stimulation, which can lead to ovarian hyperstimulation syndrome (OHSS). Guidelines recommend steps to reduce this risk, such as a GnRH antagonist protocol, a GnRH agonist “trigger” injection and freezing all embryos for transfer in a later cycle. See IVF and ICSI.

Health beyond fertility

The 2023 international guideline asks that care for PMOS cover general health as well as fertility, whether or not a pregnancy is planned. Most of the checks it recommends need only a blood test, a measurement or a few questions.

• Blood glucose. The guideline recommends a test at diagnosis and again every one to three years, depending on other risk factors for diabetes.
• Blood pressure and blood fats. The guideline recommends measuring blood pressure once a year and checking cholesterol and triglycerides at diagnosis, then according to what they show. It considers cardiovascular risk to be raised in PMOS, though low overall before the menopause.
• Weight. Many women with PMOS gain more weight over the years, for reasons not yet clear. At any weight the guideline advises a balanced diet and regular physical activity, and emphasises preventing further gain.
• The lining of the womb. Long untreated gaps between periods can let the lining of the womb thicken, and cancer of the lining is more likely with PMOS. The guideline describes the overall chance as low and does not recommend routine screening; prevention includes treatment that keeps cycles regular or a progestogen taken regularly.
• Mood. Anxiety and depression are more common with PMOS. The guideline recommends screening all adults for both, and suggests doing so at diagnosis and again as circumstances change.
• Sleep. Obstructive sleep apnoea (repeated pauses in breathing during sleep) is more common with PMOS at any weight. Snoring with unrefreshing sleep or daytime sleepiness is a reason to be assessed.
• Pregnancy. The higher chance of diabetes and high blood pressure in pregnancy, including pre-eclampsia, is why the guideline asks that PMOS be identified in antenatal care and that a glucose tolerance test be offered at 24 to 28 weeks. See preconception health.

The guideline rates the evidence as generally low to moderate in quality, and several of these recommendations rest on expert consensus.