A goitre is an enlargement of the thyroid gland. Goitres were also known as 'Derbyshire neck' due to an iodine deficiency in that area leading to swellings of the thyroid. Goitres vary considerably in size, and enlargement may be diffuse throughout the whole thyroid gland or irregular and affecting part or all of one lobe. When there are many nodules in the thyroid it is called a multinodular goitre. Goitres are described as either endemic or sporadic. In mountainous areas, such as the Himalayas, 10% of the population have goitres. These areas are known as endemic goitrous areas. The World Health Organization (WHO) has devised a simple classification, which is dependent on the size of the thyroid. The WHO goitre grading system is shown in the table below:
The WHO Goitre Grading System
This is when the goitre is not palpable or visible even when the neck is extended.
When the goitre is palpable
Goitre detected on palpation
Goitre palpable and visible when neck extended
Goitre visible when neck is in the normal position
Large goitre visible from distance
For practical reasons goitres are divided into two groups:
1) Simple - non toxic (Euthyroid)2) Toxic - (Hyperthyroid)
1. Certain substances can induce the formation of goitres. These substances are called goitrogens and are usually ions that interfere with iodide uptake by the thyroid and can therefore result in a decrease in iodothyronine production. The thyroid is then stimulated by TSH (Thyrotrophin), as there is a loss of negative feedback. This causes the gland to grow.
2. Goitres may also result from a reduced amount of iodide in the diet. Goitres are now less common as iodide is added to table salt. Large quantities of iodide have an inhibitory effect on the thyroid, but the mechanism is not fully understood.
3. Goitres can also be caused by benign or malignant tumours. Cancer of the thyroid is a very rare cause.There were only 1757 new thyroid cancer cases in the UK in 2005