# Heavy Menstrual Bleeding

URL: https://thethyroidologist.com/symptoms/heavy-menstrual-bleeding/
Section: Symptoms
Last medically reviewed: 2025-11-15

> An underactive thyroid can cause heavy or irregular periods. How thyroid disease affects menstruation and what to investigate.

Thyroid hormone influences the menstrual cycle, and an underactive thyroid is a recognised cause of heavy or prolonged periods. An overactive thyroid can cause lighter or irregular bleeding.
Because heavy periods have many causes, thyroid testing is one part of a broader assessment.

## How the thyroid affects periods

Thyroid hormone interacts with the hormones that control ovulation and the uterine lining. When thyroid levels are low, sex hormone binding globulin and other regulators change, which can lead to heavier, longer or irregular bleeding.
In an overactive thyroid, periods may become lighter, shorter or stop altogether.

## Other causes to consider

Heavy menstrual bleeding is common and often due to fibroids, adenomyosis, polyps, hormonal imbalance, bleeding disorders or medication. Thyroid disease is one contributor among many.
A clinician will assess the pattern, associated symptoms and, where needed, arrange ultrasound or blood tests.

## Investigation

Assessment includes a menstrual history, examination, thyroid function tests and often a full blood count to check for iron-deficiency anaemia. Pelvic ultrasound may be arranged.
If thyroid disease is found, it is treated and the cycle is reviewed afterwards.

## Management

Correcting thyroid dysfunction often improves flow and regularity, though this can take several cycles. Iron deficiency should be treated. Persistent heavy bleeding needs gynaecological assessment regardless of thyroid status.

## Frequently asked questions

### Can thyroid problems cause heavy periods?

Yes — hypothyroidism is a recognised cause of heavy, prolonged or irregular periods, and treating it often improves the cycle.

### Can an overactive thyroid affect periods?

Yes — it can make periods lighter, shorter or absent.

### Will my periods return to normal after treatment?

Often they improve within a few cycles, though this varies and other causes may also need attention.

### Do I need a pelvic ultrasound?

Possibly — heavy bleeding has many causes, and ultrasound is commonly used to check for fibroids, polyps or other structural problems.

## Disclaimer

The content on this website is for general educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional about your specific condition.

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