# Irregular Menstruation

URL: https://thethyroidologist.com/symptoms/irregular-menstruation/
Section: Symptoms
Last medically reviewed: 2025-11-01

> Thyroid disorders can disturb menstrual cycles — heavy, missed or irregular periods. Other causes and when thyroid testing is appropriate.

Menstrual irregularities — heavy, prolonged, missed or unpredictable periods — have many causes including PCOS, stress, perimenopause, and thyroid dysfunction.
Thyroid disorders are a recognised contributor, particularly in women with other symptoms.

## How thyroid affects cycles

Hypothyroidism commonly causes heavier, longer or more frequent periods; hyperthyroidism tends to cause lighter, less frequent periods or missed cycles. Severe dysfunction of either type can disrupt ovulation.
Thyroid dysfunction in pregnancy increases risks — preconception thyroid testing is recommended for women with irregular cycles or thyroid history.

## Other common causes

PCOS is the most common cause of irregular periods in reproductive-age women. Perimenopause, stress, significant weight change, excessive exercise, and medications (antipsychotics, chemotherapy) also disrupt cycles.
Structural problems — fibroids, polyps — can cause heavy bleeding specifically.

## When to evaluate thyroid

Thyroid testing is reasonable when irregular periods accompany hypothyroid or hyperthyroid symptoms — fatigue, weight change, temperature intolerance, mood changes — or when fertility is a concern.
Persistent irregular cycles warrant evaluation regardless of thyroid status — PCOS and other causes are common.

## Frequently asked questions

### Can thyroid problems affect fertility?

Yes — both hypo- and hyperthyroidism can disrupt ovulation and increase miscarriage risk. Thyroid testing is standard in fertility workups.

### Will treating thyroid normalise my periods?

Often yes — cycles typically improve as thyroid function normalises, though other causes may need separate treatment.

### Should I test thyroid before pregnancy?

If you have thyroid disease or risk factors, preconception testing is recommended — optimal thyroid function in early pregnancy protects fetal development.

## 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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