Thyroid problems in women: symptoms, causes, pregnancy and treatment

The thyroid is a small butterfly-shaped gland in the neck, just in front of the windpipe. The NHS says it produces hormones that affect things such as heart rate and body temperature. When it makes too little, the body's processes slow down; when it makes too much, they speed up.

Women are affected more often. The NHS notes that Hashimoto's disease, an autoimmune condition in which the immune system attacks the thyroid, is the main cause of an underactive thyroid in the UK and is most common in women, usually starting between 30 and 50, although anyone can get an underactive thyroid. An overactive thyroid is about 10 times more common in women, typically between 20 and 40.

The NHS lists common symptoms of an underactive thyroid: extreme tiredness, feeling cold, weight gain, constipation, difficulty concentrating or thinking clearly, low mood or depression, dry skin and hair or hair loss, a croaky voice, and irregular or heavy periods. They usually develop slowly and get worse over time.

Besides Hashimoto's disease, causes include other thyroid conditions such as thyroiditis, surgery or radiotherapy around the neck, treatment for an overactive thyroid, a lack of iodine (rare in the UK) and certain medicines. The NHS says you are more likely to have it if others in your family have had a thyroid condition. Treated properly it is not usually serious; untreated, or on the wrong dose, there is an increased risk of heart problems and osteoporosis, and in very rare cases myxoedema coma, an emergency needing hospital treatment.

The NHS lists nervousness, anxiety and irritability, mood swings, difficulty sleeping, persistent tiredness and weakness, sensitivity to heat, a swollen neck (goitre), an irregular or fast heartbeat, twitching or trembling, and weight loss. About 4 in 5 people with an overactive thyroid have Graves' disease, an autoimmune condition; other causes include thyroid nodules and some medicines such as amiodarone.

Complications include eye problems such as irritation, double vision or bulging eyes, pregnancy complications such as pre-eclampsia, premature birth or miscarriage, and thyroid storm, a sudden and life-threatening flare-up. The NHS says to see a GP if you have symptoms of an overactive thyroid.

Many thyroid symptoms are common to other life stages. The NHS menopause page lists changes to periods, hot flushes, sleep problems, mood changes, poor memory and brain fog and weight gain as typical of perimenopause and menopause, and the NHS palpitations page notes that palpitations can be caused by an overactive thyroid and can be a sign of menopause. Fatigue, low mood, heavier or irregular periods and weight change overlap strongly with an underactive thyroid.

This is why a simple blood test is worthwhile when symptoms are persistent: a thyroid problem is treatable, and a normal result lets other causes be explored. The NHS says that some symptoms of an underactive thyroid are common and can be caused by other conditions, but that it is important to get them checked by a GP.

For an underactive thyroid the NHS says the GP asks about symptoms and family or autoimmune history, may examine the neck, and may arrange blood tests to check the amount of thyroid-stimulating hormone (TSH) and thyroxine (T4). For an overactive thyroid, a blood test checks how well the thyroid is working and, if it is overactive, further tests may be arranged to identify the cause.

A specialist in hormonal conditions (endocrinologist) is usually involved in decisions about treatment for an overactive thyroid, according to the NHS.

An underactive thyroid is usually treated with levothyroxine tablets to replace the missing hormone, usually for the rest of your life, with regular blood tests to check the dose. The NHS says that being on the wrong dose can cause side effects such as feeling or being sick, diarrhoea, headaches or sleep problems.

An overactive thyroid is usually treatable with medicine that stops the gland making too much hormone, radioiodine treatment that destroys thyroid cells, or surgery to remove some or all of the gland. The NHS says each has benefits and drawbacks and that you will usually see an endocrinologist to decide which is best.

The NHS says that if you have an underactive thyroid and are pregnant or planning to become pregnant you should tell your GP: you will need further tests and your levothyroxine dose is likely to change during pregnancy. If it is not treated, an underactive thyroid can increase the chance of serious complications in pregnancy including high blood pressure (pre-eclampsia), birth defects, premature birth or miscarriage, though treatment usually helps prevent these.

An overactive thyroid that is not well controlled can also lead to pregnancy complications such as pre-eclampsia, premature birth or miscarriage, so planning and specialist input before pregnancy are worthwhile. Never stop thyroid medicine because you are pregnant without advice.

On the NHS, thyroid function tests and levothyroxine are provided through the GP, with referral to an endocrinologist for an overactive thyroid, complex cases and pregnancy. National charities such as the British Thyroid Foundation and Thyroid UK offer information and peer support, as the NHS notes.

Private thyroid tests and endocrinology appointments are available and can be quicker. Share results with your GP so that levothyroxine prescribing and monitoring stay consistent.