Thyroid in women: symptoms, causes, tests and pregnancy

In short: Thyroid problems are much more common in women than in men. An underactive thyroid can cause tiredness, weight gain, feeling cold and heavy or irregular periods, while an overactive thyroid can cause weight loss, a racing heart, anxiety and light periods. A simple blood test, usually TSH, checks your thyroid. See a gynaecologist or physician if you notice these symptoms, have trouble getting pregnant, or are pregnant or planning a pregnancy.

If you have been feeling tired all the time, putting on weight without reason, or your periods have changed, you may have wondered about your thyroid. You are not alone in that. Thyroid problems are common in women, and the good news is that they are easy to test for and can be managed well.

What is the thyroid, and what does it do in a woman's body?

The thyroid is a small, butterfly-shaped gland at the front of your neck, below the voice box. It makes hormones that set the pace of your body. They affect your energy, heart rate, weight, body temperature, mood, skin and hair, and your periods.

When the thyroid makes too little hormone, the body slows down. This is called hypothyroidism or an underactive thyroid. When it makes too much, the body speeds up. This is called hyperthyroidism or an overactive thyroid.

Thyroid symptoms in women

Symptoms often creep in slowly, so they are easy to put down to stress or a busy life.

Signs of an underactive thyroid:

• feeling tired and sluggish even after sleep
• weight gain without eating more
• feeling cold when others do not
• dry skin, hair fall and brittle nails
• constipation
• low mood or poor memory
• puffy face
• heavy, longer or irregular periods

Signs of an overactive thyroid:

• weight loss even while eating well
• a fast or pounding heartbeat
• feeling anxious, restless or irritable
• shaky hands
• feeling hot and sweating a lot
• trouble sleeping
• loose motions
• light or missed periods

A swelling in the neck, called a goitre, can happen with either kind, or with a normal thyroid.

What causes thyroid problems in women?

The most common cause in women is an autoimmune condition, where the body's own defence system attacks the thyroid. One kind slows the thyroid down, and another kind makes it overactive. These tend to run in families and are more common after pregnancy and in midlife. Other causes include:

• not getting enough iodine in the diet, which is why iodised salt matters
• inflammation of the thyroid, sometimes after childbirth
• thyroid nodules, which are lumps in the gland
• past surgery or treatment to the neck or thyroid

Thyroid, periods and pregnancy

Your thyroid and your periods are closely linked. An underactive thyroid can make periods heavier or irregular, and an overactive one can make them light or stop them. Either can affect ovulation and make it harder to get pregnant. If your period is late and you are not pregnant, the thyroid is one of the things a doctor checks; see our guide on late or missed periods.

In pregnancy, the baby depends on your thyroid hormones in the early months for healthy brain growth. That is why many doctors check thyroid levels when you are planning a pregnancy or at your first pregnancy visit. If you already have a thyroid condition, tell your doctor as soon as you know you are pregnant, as your treatment often needs adjusting.

After childbirth, some women develop a short-lived thyroid problem, which can look like tiredness, low mood or anxiety that is easy to blame on a new baby. Read more in thyroid imbalances after pregnancy.

What is the normal thyroid range for women?

There is no single number that fits everyone. Each lab prints its own reference range next to your result, and the range can differ in pregnancy. The main test is TSH (thyroid stimulating hormone). Your doctor may also check other thyroid hormones and antibodies. They read your results together with your symptoms, age and whether you are pregnant, so please do not judge a report on your own.

What helps alongside treatment

Thyroid conditions need a doctor's care, but daily habits support how you feel:

• use iodised salt in cooking
• eat a balanced diet with dal, vegetables, fruit, curd and whole grains
• move your body regularly, even a daily walk
• sleep well and look after your stress
• go for follow-up blood tests as your doctor advises

When to see a gynaecologist

Book a visit with a gynaecologist or physician if:

• you have several of the symptoms above for more than a few weeks
• your periods have become heavy, irregular, light or stopped
• you are trying to get pregnant and it is taking longer than expected
• you are pregnant or planning a pregnancy and have a thyroid condition or family history
• you notice a swelling or lump in your neck

Go to a doctor the same day if:

• a neck swelling is growing fast or is painful

Go to hospital straight away if:

• you have chest pain, sudden breathlessness, fainting or confusion
• a neck swelling makes it hard to breathe or swallow
• you have a very fast heartbeat with fever, confusion or vomiting
• you feel very cold, very drowsy or confused

Questions women ask

Can thyroid in women be cured?

An underactive thyroid usually cannot be cured, but it can be managed very well with long-term treatment, and most women feel completely normal. Some overactive thyroid problems and thyroid changes after childbirth can settle, and a doctor can explain what is likely in your case.

What are the first symptoms of thyroid in women?

Early signs are often vague: tiredness, weight changes, hair fall, feeling too cold or too hot, mood changes and changes in your periods. Because these are easy to blame on daily life, a simple blood test is the best way to know.

What is the normal thyroid range in women?

Each lab gives its own reference range for TSH and other thyroid hormones, printed beside your result, and the target can be different in pregnancy. Your doctor reads the numbers along with your symptoms, so ask them to explain your report.

How does thyroid affect pregnancy?

Thyroid hormones are important for your baby's growth, especially in the early months. Both an underactive and an overactive thyroid can affect fertility and pregnancy if untreated. With regular checks and treatment, most women with thyroid conditions have healthy pregnancies.

Where is the thyroid in a woman's body?

The thyroid sits at the front of the neck, below the voice box, wrapped around the windpipe. You usually cannot see or feel it. If you notice a swelling or lump there, show a doctor.