Graves' disease and overactive thyroid: symptoms, eye disease and treatment

The thyroid is a small butterfly-shaped gland at the front of the neck, just in front of the windpipe. Its hormones, thyroxine (T4) and triiodothyronine (T3), influence heart rate, body temperature and the speed at which the body uses energy. When the gland makes too much, the condition is called hyperthyroidism or thyrotoxicosis.

In Graves' disease the immune system produces antibodies that stimulate the thyroid. A hospital patient leaflet from University Hospitals Sussex explains that these antibodies react with the body's own tissue and keep the gland switched on, and that why they appear is not known. British Thyroid Foundation material describes how these thyroid-stimulating antibodies (TRAb) mimic the pituitary hormone TSH, so the thyroid keeps working even though the pituitary is trying to switch it off.

Graves' disease tends to run in families and the NHS says it mostly affects young or middle-aged women, with smoking increasing the risk. The leaflet adds that stress sometimes seems to trigger it, though in most people no clear trigger is found.

Symptoms can come on gradually or suddenly, and the NHS notes it is unlikely that anyone has all of them. Some people have mild symptoms, while for others they are severe. The hospital leaflet points out that many symptoms resemble stress or worry, and that a blood test is often needed to tell the difference, and that symptoms may have been present for months before Graves' disease is recognised.

• Nervousness, anxiety, irritability, mood swings and difficulty sleeping.

• Persistent tiredness, muscle weakness and sensitivity to heat.

• Weight loss, often despite an increased appetite.

• A fast or irregular heartbeat (palpitations) and trembling or twitching.

• Diarrhoea, needing to pee more often, persistent thirst and itchiness.

• Warm skin, excessive sweating, red palms, loose nails and patchy hair thinning.

• A swelling at the front of the neck (goitre) from an enlarged thyroid.

• Lighter or missed periods, which the hospital leaflet notes can occur in women who have them.

The usual first step is a thyroid function blood test, which measures TSH, T3 and T4. The NHS says a low TSH with high T3 and/or T4 usually means an overactive thyroid, and that what counts as normal depends on age and on the laboratory's method.

If hormone levels are high, a specialist works out why. The NHS lists a further blood test for anti-thyroid antibodies, usually found in Graves' disease, an ESR test to look for inflammation that would point to thyroiditis, and a thyroid scan, which uses a small amount of a slightly radioactive substance to look for lumps and to assess the size and shape of the gland.

NICE guideline NG145 recommends measuring TSH receptor antibodies to confirm Graves' disease in adults, and considering technetium scanning of the thyroid if those antibodies are negative. It advises ultrasound only if a nodule can be felt. The British Thyroid Foundation notes that the antibodies can be negative while a scan still confirms the diagnosis.

The NHS says an overactive thyroid is usually treatable, and that you will usually be referred to an endocrinologist who plans treatment. NICE recommends giving written and verbal information on the options so that the choice is shared. The table summarises how the three routes are described by the NHS and NICE.

The Sussex hospital leaflet says that in around 30 to 40 percent of people normal thyroid function persists after a course of tablets ends, while in the other 60 to 70 percent the thyroid becomes overactive again, usually within the first year after stopping. The British Thyroid Foundation adds that relapse is more likely if tablets are stopped while TRAb are still raised.

Radioactive iodine and surgery often leave the thyroid underactive. The NHS says this can be temporary but is often permanent, and long-term thyroid hormone replacement is then needed. Regular blood tests are therefore part of life after treatment.

Untreated or poorly controlled overactive thyroid can raise the chance of atrial fibrillation, weaker bones and heart failure, according to the NHS, which is why the condition is monitored rather than simply watched.

The NHS describes thyroid eye disease (Graves' ophthalmopathy) as affecting around 1 in 4 people with Graves' disease. Problems include dry and gritty eyes, light sensitivity, watering, blurred or double vision, red eyes, swollen or pulled-back eyelids and bulging eyes. Many people have mild symptoms that improve as the thyroid is treated, but some continue to have trouble, and severe disease can cause vision loss.

Smoking raises the risk, and the hospital leaflet says that stopping smoking is helpful. The leaflet also advises seeking urgent advice for double vision, blurred vision, or very red and swollen eyes or eyelids, since an eye specialist may need to see you. NICE notes that radioactive iodine may trigger or worsen thyroid eye disease, which is one reason eye symptoms influence the choice of treatment.

The NHS says it is very important to use contraception while taking carbimazole and for 6 months after radioactive iodine, because both can harm an unborn baby. Anyone planning a pregnancy or who becomes pregnant while on carbimazole should tell the doctor immediately. Poorly controlled overactive thyroid in pregnancy can increase the risk of pre-eclampsia, miscarriage, premature birth and low birthweight, and a clinician may switch to a different antithyroid medicine.

A thyroid storm is a sudden, life-threatening flare-up that the NHS says can be triggered by infection, pregnancy, missed medicine or damage to the thyroid. Signs include a rapid heartbeat, high temperature, high blood pressure, yellowing of the skin and eyes, severe agitation and confusion, and loss of consciousness. This is a 999 emergency.