Sudden changes in menstrual patterns—for example, a brief but very heavy “flooding” episode with clots that stops abruptly, or periods that start soaking through protection within an hour—warrant medical review. Life changes and stress can delay care, yet recurring short, heavy episodes or several missed cycles in a row should prompt assessment with a GP or gynaecologist.
When missed periods persist
If you are under 40 and miss three or more periods, book a review with your GP and rule out pregnancy first. If it is not pregnancy or a thyroid disease, clinicians consider perimenopause among other causes.
Assessment usually includes a medical history, physical and pelvic examination, and blood tests. Key hormones are oestradiol and FSH (follicle-stimulating hormone)—oestradiol tends to be low and FSH high as the body attempts to stimulate the ovaries. Abnormal results are often repeated several weeks apart to confirm the pattern.
Your doctor may also check thyroid function, prolactin and iron, and consider pelvic ultrasound. Other possible explanations include polycystic ovary syndrome (PCOS), high prolactin, significant weight change, intense exercise or stress.
One uncommon reason could be primary ovarian insufficiency or POI. It is sometimes overlooked in this age group, so clear follow-up is important.
What is primary ovarian insufficiency?
POI occurs when the ovaries stop working normally before age 40, leading to reduced oestrogen and irregular or absent periods. Around 3% of women are affected. Many cases have no clear cause.
POI can follow autoimmune conditions, chemotherapy or radiation, or exposure to certain infections or chemicals. Because bleeding may still occur, POI is not the same as premature menopause (no periods for 12 months before 40). Risk is higher with a family history of POI or prior ovarian surgery.
Common symptoms include:
- Irregular or skipped periods
- Hot flushes and night sweats
- Vaginal dryness or discomfort
- Anxiety, low mood, irritability and brain fog
- Reduced libido
- Difficulty conceiving
How does it impact health and fertility?
Pregnancy can still occur with POI, but the chance of spontaneous conception is low (under 10%). Use contraception if you do not wish to conceive. If pregnancy is a goal, early referral to a fertility specialist can improve options.
Losing oestrogen years before the average age of menopause increases long-term risks, including low bone density, fractures and cardiovascular disease, and can contribute to urogenital symptoms, sleep disturbance and mood changes.
Many people with POI benefit from menopausal hormone therapy (MHT/HRT) unless there is a contraindication. Treatment is usually continued until at least the average age of natural menopause. Discuss the plan, monitoring and follow-up with your GP or gynaecologist.
Can HRT cure POI?
When primary ovarian insufficiency (POI) is diagnosed or menopause occurs before age 40, menopausal hormone therapy is usually recommended for long-term health unless there is a contraindication.
Replacing oestrogen and adding a progestogen if the uterus is present helps protect the heart, bones and brain, and reduces menopause symptoms such as hot flushes, night sweats and sleep disturbance. POI increases the risk of low bone density, fractures and cardiovascular disease, and the longer oestrogen remains low, the greater the risk.
Many people worry that HRT raises the chance of breast cancer or heart disease. In younger women with POI, appropriately prescribed HRT is not generally linked with increased risk, and the greater health risk is often not treating prolonged oestrogen deficiency. Decisions should be individualised with a GP or gynaecologist.
Typical approach
- Oestrogen replacement (often transdermal)
- Progestogen for endometrial protection if the uterus is present
- Continue until at least the average age of natural menopause, then review benefits and preferences
However, monitoring is important to ensure the safety of this procedure. Regular review of symptoms, blood pressure and cardiovascular risk. Create a bone health plan that includes increasing intake of calcium, vitamin D, resistance exercise and bone density scans as advise. You also need to check for contraindications and interactions with existing medicines
Whether to continue HRT into the 50s is a personal choice. Some people opt to continue to prevent the return of hot flushes, sleep issues and vaginal symptoms, while others taper. Review the plan each year and adjust to suit health goals and quality of life.
Bottom Line
Sudden flooding, several missed periods under 40 or ongoing cycle changes deserve a proper check. Ask your GP or gynaecologist to rule out pregnancy and thyroid problems, then consider POI alongside other causes. If tests confirm POI and there is no contraindication, menopausal hormone therapy can protect heart, bones and brain until at least the average age of natural menopause.
With timely diagnosis and a tailored plan, most people can manage symptoms, safeguard long-term health and make confident decisions about fertility and future care.
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