What it is
PMOS is a common hormonal condition affecting the ovaries, periods, fertility, skin and metabolism. It affects about 1 in 8 women of reproductive age. It was called PCOS (polycystic ovary syndrome) until it was renamed in 2026; many clinics still say PCOS. The ovaries hold many small follicles, not harmful cysts. There are three threads: disrupted ovulation (no egg released each month), raised androgen (male-type) hormones such as testosterone, and underlying insulin resistance.
Symptoms to look out for
- Irregular, infrequent or absent periods
- Difficulty getting pregnant
- Acne, excess facial or body hair, or thinning scalp hair
- Weight gain, especially around the waist
- Dark skin patches in the armpits or neck, and skin tags
- Loud snoring and unrefreshing sleep
What causes it
Insulin resistance is thought to be the key driver in most women: the body needs more insulin than usual, so insulin levels rise. High insulin pushes the ovaries to make more androgens and disrupts ovulation. There is a strong family link, and it occurs at all body sizes. Poor sleep and stress can make it worse.
Improving insulin sensitivity can break the cycle
High insulin makes the ovaries produce more androgens, and promotes weight gain around the waist, which raises insulin further. Reducing insulin resistance can break this loop: periods often become more regular, ovulation and fertility improve, and skin and hair symptoms ease, in lean women too.
What you can do
- Food. Cut sugary drinks and ultra-processed snacks. Build meals with plenty of protein and non-starchy vegetables, and keep starchy carbohydrate to smaller amounts. Even modest weight loss often brings back more regular periods and ovulation. See the Metabolic Health 28 Day Plan at healthshelf.org/28-day-plan.
- Movement. At least 150 to 300 minutes a week of moderate activity such as brisk walking, plus muscle-strengthening on two days a week.
- Sleep and stress. Aim for 7 to 9 hours of sleep, and keep a regular schedule. Brief daily relaxation helps lower stress.
- Supplements. Inositol is a personal choice: little harm, but limited proven benefit. Check any supplement with your clinician.
Medicines
Metformin improves insulin sensitivity and can help periods and ovulation. Weight-loss injections may be considered for a higher weight, with reliable contraception. The combined pill regulates periods and reduces androgen symptoms when not trying to conceive. Anti-androgen medicines help hair and acne but need effective contraception. Most are not licensed for PMOS but are used on the evidence, with medical supervision.
When to get help
- See a doctor about irregular or absent periods, troublesome acne or excess hair, or difficulty getting pregnant.
- Ask for a check of your metabolic health: blood sugar, blood fats and blood pressure. Blood sugar is re-checked every one to three years and blood pressure every year.
- If you are planning a pregnancy, ask for a pre-conception review, as some medicines must be stopped first.