Graves' Disease
Graves' Disease is the most common cause of thyrotoxicosis, accounting for about 70% of cases in Australia. It can occur at any age, although it is most common in young women between 20 and 40 years of age. It affects approximately 1 in 100 of the adult population, but females are five to 10 times more likely to get Graves' disease than men.
Fig.1: Robert Graves, Irish physicianThe disease was first described by an English physician named Caleb Parry in 1786, but he failed to publish his findings during his lifetime. In the English-speaking world the disease is instead named after the Irish physician Robert Graves who described it in 1835 (Fig. 1), while the Europeans know it as Basedow's disease, following von Basedow's description of his findings in Germany in 1840.
The cause of Graves' disease is not fully understood, but it is likely to be a combination of genetic and environmental factors. For example, there is some evidence of a connection between vitamin D deficiency and the development of Graves' disease. In addition, smokers are more likely to develop Graves' disease than non-smokers. According to an article in the Journal of the American Medical Association in 1993 smokers are twice as likely as nonsmokers to develop Graves' disease. Smoking also worsens eye problems in people with Graves' disease, and reduces the effectiveness of treatments for thyroid eye disease.
Graves' disease is an autoimmune disease, like Type 1 diabetes and rheumatoid arthritis, where the body's immune system forms antibodies to attack its own organs. In the case of Graves' disease, the immune system attacks the thyroid, with production of thyroid stimulating antibodies, which bind to the TSH receptor (anti-TSH receptor antibodies). The autoantibodies stimulate the thyroid cell to make excess thyroid hormone, which results in a state of thyrotoxicosis.
The thyroid tends to be diffusely enlarged although nodular varieties of Graves’ disease do exist. Spontaneous exacerbations and remissions of Graves' disease can occur. The environmental triggers are still not well characterised, but postpartum (after pregnancy) exacerbation is common. Excess iodine can precipitate active Graves' disease by providing more substrate for hormone synthesis and possibly also by disturbing immune function.
Presentation
The symptoms and signs of Graves' Disease can be divided into two by the symptoms related to particular aspects of the disease process:
1) Symptoms due to stimulation of metabolic processes and the sympathetic nervous system
Hypermetabolism symptoms such as palpitations, tremor, irritability, weight loss, etc. (see Thyrotoxicosis Overview), although in the elderly the cardiac and neurological symptoms tend to predominate. Eye changes of lid lag and lid retraction, commonly found in all forms of thyrotoxicosis, are caused by sympathetic nerve stimulation of the upper eyelid muscles.
2) Symptoms due to the autoantibodies.
Specific to Graves' disease is Graves' Ophthalmopathy (Thyroid Eye Disease - TED), which is distinct from the lid lag and lid retraction common to all forms of thyrotoxicosis. TED is thought to be caused by reaction to antigens in the retroorbital tissues (behind the eye) that cross react with the TSH receptor, resulting in swelling of the orbital contents, lids and periorbital tissues, with marked lid retraction, vision effects and a characteristic stare (Fig. 2).
Ophthalmopathy is much more common in smokers (who should be strongly advised to quit), and in 10% of patients can be unilateral (affect only one eye).
Fig.2: Thyroid eye disease showing characteristic stare
Fig. 4: Thyroid scan of Graves diseaseDiagnosis
The diagnosis of Graves' disease is made by a combination of clinical suspicion, blood tests and scanning:
- Thyroid function tests
In classical cases, both T3 and T4 are elevated and the TSH is suppressed (Fig. 3) - Thyroid Autoantibodies
Autoantibodies against the TSH receptor (90%) and antithyroglobulin and peroxidase antibodies (80%) - Radioactive Iodine or Technetium Scan
This will show a uniform increased uptake of the tracer throughout the gland in Graves' disease (Fig. 4).
Fig. 3: Typical thyroid function tests of thyrotoxicosis
Treatment
It is important to realise that Graves' Disease is self-limiting in about 50% of cases. Persistence or recurrence of Graves' disease is more likely when there is a previous history of recurrent disease, in the presence of a large goitre, when T3 excess persists despite control of T4 with thionamide therapy (carbimazole), and when TSH-receptor antibody persists during thionamide therapy.
The available treatments are the same as any for thyrotoxicosis, detailed on their own webpages elsewhere (click on the names for links to more information):
a) Antithyroid Drugs
The main antithyroid drugs used are the thionamides, the most common drug in this group being carbimazole (Neomercazole). This drug interferes with reactions that take place in the synthesis of iodothyronine.
Most patients with Graves' disease require short-term (several months) treatment with an antithyroid drug (thionamide) before consideration of longer-term or definitive therapy. Typical starting doses are 15-20mg daily for mild to moderate hyperthyroidism, 30-40mg for severe cases. Once under control, doses can be decreased to maintenance levels (5-10mg per day).
Prolonged thionamide therapy (12–18 months in a first episode) avoids the disadvantages of surgery and radioiodine, and seems to give the best chance of sustained remission. Nonetheless, the risk of relapse when the drug is stopped is greater than 50%.
b) Beta-Adrenergic Blockers
Typically propranolol is used to help control some of the disabling symptoms; these drugs are used initially for the tachycardia and tremors as a result of the iodothyronines potentiating the effects of the catecholamines.
This is the treatment of choice for most patients, and is given orally as 131I. The principle of this treatment is that the thyroid is the only tissue in the body to take up iodine, so that the radioactive iodine can selectively kill the cells that take up the iodine without causing any harm to the body. It avoids the potential complications of surgery, but rarely renders the patient euthyroid after treatment, and is more likely to result in hypothyroidism (low thyroid function).
Radioactive iodine should not be used in patients with severe TED as the eye disease can worsen in about 15% of patients following treatment.
Surgery to remove the thyroid, in the form of a total thyroidectomy, is indicated in some patients where there is compression of the trachea, the patient has relapsed after drug treatment or is unable or unwilling to have radioactive iodine.
It is also the quickest way of rendering the patient euthyroid (normal thyroid function), as RAI may take up to six months and a second dose to achieve the desired result.
Total thyroidectomy is also favoured over radioactive iodine when eye disease is present, as 15% of patients can worsen their disease after radioactive iodine. Surgery also has the advantage of reducing anti-TSH receptor antibody levels better than RAI over the long term, potentially reducing their impact on eye disease.
Subtotal thyroidectomy (leaving some thyroid tissue behind at operation) as a surgical option has been superseded as it leads to unacceptable results in 30% of patients: the recurrence rate of thyrotoxicosis is 8-25%, and 30-50% develop hypothyroidism after subtotal thyroidectomy. In experienced hands there is no difference in complication rates when a total thyroidectomy is performed, and patients have certainty about their thyroid status.
Which Treatment Is Right?
While each modality is satisfactory in rendering the patient euthyroid (normal thyroid function), none is ideal as all have a risk of adverse effects and none but total thyroidectomy eliminates the risk of recurrence. Although total thyroidectomy virtually eliminates this risk, it is at the cost of definitely needing life-long thyroid hormone replacement, but many patients find this gives them greater certainty than long-term blocking drugs or radioactive iodine.
Selecting treatment for an individual depends on many factors, not least being patient choice and physician bias. In the United States, radioiodine is the preferred primary modality, but in Europe and Australia, antithyroid drug therapy is preferred for patients with a first episode of Graves' hyperthyroidism, ahead of radioiodine and, lastly, surgery.
Changes after treatment
Having thyrotoxicosis makes you feel that you have lots of energy and drive, but it comes at the expense of the health of your heart and bones particularly. It is like over-revving the engine of a motor car; it may make you go faster for a while, but it wears out the engine faster too and you are more likely to crash!
When you are treated by any of the measures mentioned on these webpages, and your body's metabolism is brought back under control, you must expect some changes, some of which can be quite distressing for a time. These changes are more noticeable if you are having surgery for your thyrotoxicosis, as the effect is more abrupt, and thyroid function returns to normal much more quickly than with the other treatments. The changes are also more marked if you are still a little toxic at the time of your operation.
It is very common to feel tired and lethargic after the treatment, as you must get used to being "normal" again; a small amount of weight gain is also common, but usually no more than about 3 kg, and of course if you are prepared for it to happen, you can prevent the weight increase by raising your exercise levels and altering your diet to adjust to the new circumstances.
These symptoms can be very distressing at first, but gradually wear off with time as you adjust to the way your body should be functioning. Of course I will also check your thyroid function with a blood test, after surgery or other treatment, to make sure you have enough replacement tablets, or enough residual function in the remaining thyroid.