Hashimoto's thyroiditis: symptoms and treatment

In Hashimoto's disease the immune system attacks the thyroid gland, so the gland cannot make enough thyroid hormone. The result is an underactive thyroid (hypothyroidism). The NHS calls it the main cause of an underactive thyroid in the UK.

The British Thyroid Foundation explains that thyroid antibodies develop when the immune system mistakenly attacks thyroid cells, causing inflammation, tissue damage or disrupted function. Antibodies can also be present in people without thyroid disease.

The NHS says symptoms usually develop slowly and get worse over time, and can be mild and hard to notice. They are not specific to the condition, so a blood test is needed to tell. NICE CKS note that in older people they may be especially mild.

• Feeling extremely tired.

• Feeling cold more than usual.

• Putting on weight.

• Constipation.

• Difficulty concentrating or thinking clearly.

• Low mood or depression.

• Dry skin, dry hair or hair loss.

• A croaky voice.

• Irregular or heavy periods.

The British Thyroid Foundation says the most obvious signs in children can be slow growth and gaining weight despite eating healthily. It can also delay puberty, although in rare cases it brings on early signs of puberty. Children are referred to a paediatric endocrinologist, start levothyroxine for life, and have the dose adjusted as they grow.

The charity says symptoms should ease within three to six months of starting treatment, and that testing can be every six weeks for a very young child until levels settle. Once an adult with stable treatment, a yearly blood test is normal, under the GP.

A GP will ask about symptoms, family history of thyroid or other autoimmune disease, and recent pregnancy, and may feel the neck for swelling. The NHS says blood tests check thyroid-stimulating hormone (TSH) and thyroxine (T4). NICE CKS say overt hypothyroidism means TSH above the reference range, usually above 10 mU/L, with low free T4.

Subclinical hypothyroidism means a raised TSH with normal T3 and T4. Secondary (central) hypothyroidism, from a pituitary or hypothalamic problem, has low or normal TSH with low free T4 and is referred urgently to an endocrinologist.

TPO antibodies are used to confirm an autoimmune cause. The British Thyroid Foundation says a positive result means the underactive thyroid is autoimmune. It also notes about 10% of people without a thyroid disorder have them. They usually only need testing once, because levels rarely change treatment.

The NHS says treatment replaces the hormone your body cannot make, usually as levothyroxine tablets, and you will usually need them for life to prevent symptoms returning. NICE CKS advise starting levothyroxine alone, reviewing symptoms and thyroid tests every 3 months with dose changes if needed, and then checking TSH once a year when stable.

Too much levothyroxine can cause side effects. The NHS lists feeling or being sick, diarrhoea, headaches and problems sleeping, and says to speak to your GP or a pharmacist if you have any. If symptoms persist despite adequate doses, CKS advise looking for other causes and considering referral to endocrinology.

Some people ask about extra thyroid hormone (T3) or supplements. The British Thyroid Foundation lists a webinar on T3 research and a page on diets and supplements, so ask your clinician before starting anything yourself.

With the right dose, the NHS says an underactive thyroid is not usually serious. Without treatment, or on the wrong dose, heart problems and weakened bones become more likely. NICE CKS list dyslipidaemia, metabolic syndrome, coronary heart disease, stroke and heart failure among the complications.

In pregnancy, untreated disease increases the chance of pre-eclampsia, birth defects, premature birth or miscarriage, says the NHS, and treatment usually helps prevent them. NICE CKS advise specialist referral for women who are planning a pregnancy, pregnant, or postpartum and treated with levothyroxine.

Having Hashimoto's slightly raises the chance of another autoimmune condition, such as Addison's disease, pernicious anaemia or coeliac disease, though the British Thyroid Foundation says the risk is small.

The NHS says that in very rare cases a severe underactive thyroid can lead to myxoedema coma, a life-threatening emergency that needs hospital treatment and is more common in older people. Call 999 for confusion, collapse or extreme drowsiness. See a GP if symptoms return while on treatment, as your dose may need checking.

Most adults are diagnosed and monitored by their GP, with referral to an endocrinologist when the cause is unclear, symptoms continue despite treatment, or pregnancy is involved. Children go to a paediatric specialist. Private endocrinology can offer longer or earlier appointments, but day-to-day dose monitoring is still a repeated blood test, so ask which results the clinic will share with your GP.