When the immune system keeps the thyroid switched on in Graves Disease

Graves’ disease is the most common autoimmune cause of an overactive thyroid. It develops when the immune system produces antibodies known as TSH receptor antibodies, or TRAb.

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These antibodies attach themselves to the thyroid’s TSH receptors and imitate the signal normally sent by the pituitary gland. They are rather like counterfeit keys that fit the lock surprisingly well. The thyroid continues producing T4 and T3 even though the body is already trying to turn production down.

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The result is hyperthyroidism: too much thyroid hormone circulating through the body.

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What might you notice

Thyroid hormones influence almost every organ, so Graves’ disease can produce a surprisingly varied collection of symptoms:

• Palpitations or a fast and sometimes irregular heartbeat

• Shaking, sweating and intolerance of heat

• Weight loss despite a normal or increased appetite

• Muscle weakness and reduced stamina

• Anxiety, irritability or difficulty sleeping

• Frequent bowel movements

• Lighter or irregular periods

• An enlarged thyroid gland known as a goitre

 

Some people feel intensely restless; others mainly notice exhaustion. Running the body too quickly is tiring work. Untreated or poorly controlled Graves’ disease can increase the risk of atrial fibrillation, heart failure, bone loss and, rarely, thyroid storm. Fortunately, effective treatments are available.

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Graves’ disease and the eyes

Some patients develop thyroid eye disease, causing grittiness, watering, light sensitivity, swelling around the eyes, a staring appearance or double vision.

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Thyroid eye disease is caused by the autoimmune process affecting tissues behind the eyes. It is not simply the result of a high thyroid hormone level and may follow a different course from the thyroid itself.

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Smoking considerably increases its risk and severity. New double vision, difficulty closing the eyelids or any change in vision should be assessed promptly.

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How is Graves’ disease confirmed

Blood tests usually show:

• A low or suppressed TSH

• Raised free T4, free T3 or both

• Positive TSH receptor antibodies

 

T3 can sometimes be disproportionately elevated, which is why looking only at TSH and T4 may miss part of the story. A thyroid scan may be helpful when the antibody result is negative or the cause remains uncertain. Ultrasound is generally reserved for patients with a thyroid nodule, a large goitre or another structural concern.

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How is it treated

A beta blocker may first be prescribed to reduce palpitations, tremor and other adrenaline-like symptoms. This can make the body feel calmer quite quickly, although it does not treat the underlying thyroid overactivity.

 

The three main treatments for Graves’ disease are:

Anti-thyroid medication

Carbimazole reduces the production of new thyroid hormone. A usual course lasts approximately 12 to 18 months and gives the immune system an opportunity to settle. Some patients achieve lasting remission. Others relapse and may choose another course, long-term low-dose treatment, radioiodine or surgery.

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Radioactive iodine (RAI)

The thyroid naturally collects iodine. Radioactive iodine uses this property to gradually disable overactive thyroid cells. It is usually given as a capsule or drink and avoids an operation, but its full effect takes several weeks or months. Hypothyroidism is expected afterwards in most patients and requires lifelong levothyroxine. Radioiodine is unsuitable during pregnancy or breastfeeding and can worsen thyroid eye disease in susceptible patients.

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Thyroid surgery

Total thyroidectomy removes the source of excess thyroid hormone and provides rapid, reliable control.

It may be favoured when there is a large goitre, pressure in the neck, a suspicious thyroid nodule, significant eye disease, a need for rapid definitive treatment or pregnancy plans that make radioiodine inconvenient.

Surgery carries anaesthetic and operative risks and results in lifelong dependence on levothyroxine. When chosen, it should ideally be performed by an experienced, high-volume thyroid surgeon.

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Choosing the right treatment

There is no universally correct treatment for Graves’ disease. The balance may be influenced by:

• The severity of the hyperthyroidism

• Thyroid size and the TRAb level

• The likelihood of remission

• Thyroid eye disease and smoking

• Previous reactions to medication

• Other medical conditions

• Pregnancy plans

• Caring responsibilities and the practicality of radiation precautions

• Whether preserving the thyroid is an important personal priority

 

The best decision is therefore made with the patient rather than simply handed to them.

 

Graves’ disease and pregnancy

Graves’ disease should ideally be stable before conception. Radioiodine must never be used during pregnancy, and pregnancy must be postponed for at least six months after treatment and until thyroid function is stable. When antithyroid treatment is required, propylthiouracil is generally preferred around conception and during the first trimester. Carbimazole is commonly used later, under specialist supervision. Treatment aims to use the lowest effective dose because antithyroid medicines cross the placenta. TRAb can also cross the placenta, even in someone who previously had radioiodine or thyroid surgery. Antibody monitoring may therefore be needed during pregnancy.

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One important rule when taking carbimazole

If you develop a fever, significant sore throat, mouth ulcers or flu-like illness while taking carbimazole or propylthiouracil, stop the tablets and obtain same-day medical advice and an urgent blood count. These symptoms may indicate agranulocytosis, a rare but potentially serious fall in infection-fighting white blood cells.

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Understanding the treatment choices

The differences between tablets, radioiodine and surgery deserve more than a hurried list at the end of a consultation.