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Thyroid problems and your cycle
Revisado: 4 de octubre de 2026
Solo en inglés por ahoraYour thyroid helps control how your body uses energy, and it affects your periods too. Too much or too little thyroid hormone can make periods lighter, heavier or irregular.
What the thyroid does
The thyroid is a small, butterfly-shaped gland at the front of your neck. It makes hormones that control your metabolism, which includes how fast your body uses energy and how fast your heart beats. Thyroid problems are common in women: about 1 in 8 women will have one during their life. An underactive thyroid (hypothyroidism) makes too little hormone. An overactive thyroid (hyperthyroidism) makes too much.
How it can change your periods
Thyroid hormone levels that are too high or too low can change your periods. They may become much lighter, much heavier or irregular. An underactive thyroid can cause irregular or heavy periods. Thyroid problems can also make periods stop for several months or longer (amenorrhoea). When your cycle is affected, ovulation (the release of an egg) is affected too, so it can be harder to get pregnant. Thyroid disease is also linked to the ovaries stopping working before age 40 (premature ovarian insufficiency).
Signs of an underactive thyroid
Symptoms usually come on slowly and get worse over time. They can include feeling very tired, feeling cold when others do not, weight gain, constipation, low mood, dry skin, dry or thinning hair, a hoarse voice and trouble concentrating. In the United States, the most common cause is a condition called Hashimoto's disease. It is most common in women and usually starts between the ages of 30 and 50.
Signs of an overactive thyroid
An overactive thyroid is about 10 times more common in women than men, and it usually starts between ages 20 and 40. Signs include feeling nervous, anxious or irritable, trouble sleeping and a fast or irregular heartbeat. You may also have shaking hands, sweat more, find heat hard to cope with, feel tired, or lose weight even when you eat as much as usual. Some people have a swelling in the neck. The most common cause is Graves' disease, where the immune system makes the thyroid produce too much hormone.
Tests and treatment
A blood test can show how well your thyroid is working. It measures thyroid-stimulating hormone (TSH) and sometimes thyroid hormone (T4). An underactive thyroid is usually treated with tablets that replace the missing hormone. Most people take them for life, with regular blood tests to check the dose. An overactive thyroid can be treated with medicines that stop the thyroid making too much hormone, with radioiodine treatment (a type of radiotherapy), or with surgery to remove some or all of the thyroid.
When to see a doctor or nurse
See a doctor or nurse if your periods change, for example becoming much heavier, lighter or irregular, especially if you also have other signs of a thyroid problem. Also get checked if you have had no period for 3 months and are not pregnant or breastfeeding, or if you are finding it hard to get pregnant. If you have a thyroid condition and are pregnant or planning a pregnancy, tell your care team, as thyroid problems in pregnancy can affect you and your baby. Tracking your periods and symptoms in Ciclo can help show what has changed. If you have an overactive thyroid and your symptoms suddenly get much worse, get emergency help, as this can be a rare but life-threatening flare-up.
This is general information, not a diagnosis. If your periods change and you also feel unwell, ask a doctor or nurse about a thyroid blood test.