Alternative names for multinodular goitre
Multinodular goiter; MNG; nodular goitre.
What is multinodular goitre?
The thyroid gland is a butterfly-shaped gland sitting in the front of the neck. It is responsible for the production and release of thyroid hormones. Any increase in the size of a part or whole of the thyroid gland is called a goitre. For more information see the article on goitre. A multinodular goitre is a goitre where there are many lumps (nodules) that appear within the gland. This is probably the most common thyroid gland disorder. Nodules may be clearly visible or only discovered through examination or scans.
What causes multinodular goitre?
Worldwide, the common reason for goitre to occur is because of a lack of iodine known as iodine deficiency. In order to absorb as much available iodine from the bloodstream as possible, the thyroid as a whole gets bigger due to an increase in thyroid cells. In the UK, people usually get enough iodine in their diet, not necessarily because their diet is healthier but because of the types of food they eat. This means that there must be other, largely unknown factors which cause multinodular goitre.
The thyroid gland is under the control of the pituitary gland and a hormone produced by this gland, called thyroid stimulating hormone, causes the thyroid to work harder and grow in size. Over a period of time, nodules are formed due to different rates of growth in different parts of the gland, possibly combined with other external influences such as diet, drugs or genes. The nodules lead to an irregular knobbly appearance in the structure of the thyroid gland. This process takes many years, so it is common to find an increase in the number of people with multinodular goitre as people become older.
What are the signs and symptoms of multinodular goitre?
In many cases, multinodular goitres appear and can be visible even if the thyroid is working normally (known as euthyroid). Usually, multinodular goitre is not visible and is only discovered when a patient is being examined or scanned for other reasons. Where there are symptoms of an overactive (hyperthyroid) or underactive (hypothyroid) thyroid gland, nodules are often found. (See the articles on thyroid hormones and thyrotoxicosis).
Less commonly, multinodular goitre can cause pain or discomfort from a rapid increase in size. This may be due to a sudden build-up of fluid or blood within a nodule or, more rarely, due to a tumour. Other symptoms can include breathing difficulty or a harsh noise on breathing because of pressure on the windpipe, swallowing difficulty from pressure on the food pipe or hoarseness of the voice due to pressure on the nerve controlling the vocal cords. These last few symptoms need urgent medical assessment.
How common is multinodular goitre?
The World Health Organisation estimates that goitre affects 12% of the population worldwide, with the figure being slightly lower across Europe. Multinodular goitre and thyroid disease in general, are very much more common in women. There is also clear evidence of an increase with age, partly due to the fact that multinodular goitre is formed over a long period of time. Ultrasound examination of the thyroid gland will reveal nodules in about 50% of women aged 50 or over. There is no reason for most patients to worry about such a normal finding and, as long as the thyroid gland is working normally, many people will not require medical treatment.
Is multinodular goitre inherited?
Some forms of goitre can be inherited. There is some evidence that the presence of goitre in one family member increases the chances of other family members having goitre. However, our knowledge of genes and genetic problems is growing all the time and more precise information is likely to be available in the future, including the effects of specific genes and the environment on goitre.
How is multinodular goitre diagnosed?
Apart from taking an initial thorough family and medical history, the patient’s GP will also examine for physical symptoms and test hormone levels in the blood. In some cases, patients may then be referred to see a surgeon, a thyroid specialist or an endocrinologist. For details on further tests, see the article on goitre.
How is multinodular goitre treated?
It is important to establish whether or not the thyroid gland is functioning normally. Most patients will have a normally functioning, but lumpy thyroid gland that will never harm them.
Regular monitoring of thyroid function would probably be the treatment if function is normal (euthyroid) and the goitre is not causing any local structural problems (for example, compressing the food pipe or wind pipe or the nerve that controls the voice box), and if there is no concern about any abnormal areas within the gland. If there were any structural problems, these would usually be apparent in the ultrasound scan performed at the time of diagnosis. Other tests or treatment would be recommended if there was a change in this situation.
In the case of an underactive thyroid (hypothyroidism) with no other symptoms of concern, thyroxine therapy would be given which may, over a period of time, help to slightly reduce the goitre’s size, especially in cases where there is a history of iodine deficiency.
In the case of an overactive thyroid (hyperthyroid), the terms ‘toxic multinodular goitre’ or ‘multinodular goitre with thyrotoxicosis’ may be used. This overactivity may be subtle and picked up only in blood tests (this is called ‘subclinical thyrotoxicosis’), or clearly overactive (see the article on thyrotoxicosis). Tablets, such as carbimazole, can be used in the short-term to control secretion of thyroid hormones while the diagnosis is being established and further treatments are being considered.
Treatment with drugs such as carbimazole can help control thyroid overactivity but this does not lead to a cure, and thyroid overactivity is likely to return if the treatment is stopped. In such instances, surgical treatment or radioactive iodine treatment (also known as radioiodine) may be considered for a more permanent treatment of overactive thyroid. Some patients opt to continue carbimazole over the long-term to control overactivity.
If any abnormal areas are found on the scan in the multinodular goitre, a tissue sample may be taken during the scan for further testing using a fine needle. This result will determine which treatment is offered.
Most patients need no treatment. Occasionally, surgery to remove all or most of the thyroid can be carried out, particularly if a multinodular goitre is large and the patient feels it is unsightly. However, removing a normally functioning gland can leave a patient requiring thyroxine for life. Radioiodine can be used to treat an overactive thyroid where surgery is not preferred by the patient.
For further treatment options see the article on goitre.
Are there any side-effects to the treatment?
The side-effects are the same as those for the treatment of goitre.
What are the longer-term implications of multinodular goitre?
Usually, multinodular goitre which is not causing any symptoms, is likely to continue causing no bother. However, over a period of time, there is a possibility that it can lead to either an underactive or an overactive thyroid. Goitre, or individual nodules, could also increase in size to the point where pressure affects the area around the thyroid gland.
Written: March 2011