THYROID & PARATHYROID PROBLEMS
Thyroid Nodules & Goitres
Goitres and Nodules
Enlargement of the thyroid gland is extremely common. Most causes are entirely benign and will need no treatment.
What is a Goitre and what is a nodule?
Before we go on to talk about some of the more common causes of thyroid enlargement it is important that we first talk about some of the commonly used terms that doctors and patients use to describe enlarged thyroid glands.
Goitre is a generalised enlargement or swelling of the thyroid gland. It can be described as diffuse, meaning generalised swelling affecting all of the gland, or multi-nodular with lots of discrete lumps (nodules) in the gland.
Nodules are discrete lumps within the thyroid gland. They can be single or multiple. If there are lots of them they can cause overall swelling of the gland causing a type of goitre known as a multi-nodular goitre (MNG). A dominant nodule is the largest nodule within a multi-nodular gland.
Nodules in the thyroid gland are extremely common, upto 60% of the population has them. Modern ultrasound machines are able to detect nodules even when they only measure a few millimetres. The thyroid gland has a tendency to become more nodular as you get older especially if you are female. Many benign thyroid diseases such as hypothyroidism can also lead to a multinodular or diffuse goitre. The vast majority of these nodules are completely benign. Only rarely are they a sign of anything worrying such as a thyroid cancer. A careful history and examination by a thyroid specialist is often all that is required, sometimes further tests such as ultrasound and needle biopsy are required to decide whether individual nodules may be cancerous.
What are the causes of thyroid enlargement?
Physiological – sometimes during your life for example during puberty or pregnancy the body requires extra thyroid hormones this can put an extra strain on the thyroid gland and cause it to enlarge.
Dietary – insufficient iodine in the diet. This used to be common in mountainous or coastal communities where there is little iodine in the soil. Again the thyroid has to work harder to produce hormones and can enlarge. This is called Endemic Goitre. It is less common these days due to dietary supplements and particularly to the use of iodised salt. Some foods if eaten in excess can interfere with iodine absorption e.g. kale, cauliflower.
Dyshormonogenesis – these are inherited conditions where the body lacks the necessary enzymes that are required to make thyroid hormones leading to hypothyroidism and a goitre. These problems may run in families. Some drugs may also interfere with hormone production e.g. Amiodarone, Lithium.
Auto-immune Thyroiditis – Graves’ disease, Hashimoto’s Thyroiditis. These are auto-immune disease where the body makes antibodies that mistakenly attack its own cells. These are called auto-antibodies. In Grave’s disease this causes an overactive gland and a goitre. In Hashimoto’s Disease there is more commonly a hypothyoidism and a goitre.
Thyroiditis- this is inflammation of the thyroid gland and may be autoimmune as above other rare causes can be infections and Riedel’s Thyroiditis.
Multinodular Goitre (see below)
Nodules within the thyroid gland are extremely common, up to 40% of the population, they are more common in females and you get more of them as you get older. You cannot see or feel the thyroid gland in most people. Most thyroid nodules cannot be felt and are detected only on ultrasound or other tests. Nodules that you can feel (called Palpable nodules) usually measure more than 2cm and are present in around 7% of the population. Only one in twenty of these palpable nodules are cancerous. Much more common causes are benign colloid nodules, multinodular goitre and thyroid cysts.
What are the symptoms of thyroid nodules?
Most nodules are asymptomatic and are increasingly picked up during investigations of other problems, MRI scans for neck pain seem to be the main culprit. Most patients once they find out they have thyroid nodules are concerned that they may have thyroid cancer. Multinodular goitres and some very large nodules may press on surrounding structures such as the windpipe or the oesophagus leading to shortness of breath or swallowing difficulty. This is especially true if they extend behind the collarbone (sternum) and down into the chest (a Retrosternal Goitre). Rarely thyroid cancers can affect the nerves that move the voice box causing changes in the voice and hoarseness, occasionally a large benign goitre may stretch the nerve leading to voice changes but this is unusual. Large goitres and nodules may also be visible and patients may have cosmetic concerns.
How do I find out if my nodules are benign?
Your doctor should perform the Triple Assessment for any thyroid nodule. That is 1) Take a thorough history 2) Examine your neck and thyroid gland and 3) Obtain any additional tests that may be needed.
Even before any further tests are carried out there are some factors that make it more likely that a nodule is suspicious for cancer. It is important to realise that not all patients with nodules who fall into these categories will have thyroid cancer but it would mean that further investigation of thyroid nodules is more likely to be required. These factors are:
Patient Factors that make a nodule more likely to be suspicious
Additional Tests for Thyroid Nodules
As well as the risk stratification factors above most patients will undergo additional tests, the most useful of which are:
FNAC (fine needle aspiration cytology)
This is an extremely useful investigation in the hands of expert cytologists and can help greatly in the differentiation of cancer from benign nodular disease. A negative FNAC however does not exclude the presence of malignancy especially in a larger nodule (>3cm).
It allows the differentiation of solitary nodules versus dominant nodules within a multinodular goitre (10% vs 6% risk of malignancy). It may also detect features suggestive of malignancy such as calcification, cervical lymphadenopathy or invasion of the thyroid capsule. If used to direct fine needle aspiration it increases the accuracy of cytological diagnosis.
Thyroid function tests and antibody screen
CT scan (none contrast enhanced) especially useful if there is suspicion of retro-sternal extension.
Management of nodular thyroid disease
There are a number of indications for surgery in nodular thyroid disease.
1. Exclusion of malignancy. Even with the above tests it is sometimes not possible to exclude malignancy without excision of the nodule. This is especially true for patients who have any of the risk factors above.
2. Compressive symptoms.
3. Cosmetic concerns. This is a common factor in younger patients however it is extremely important that these patients are counselled about the possibility of complications following surgery.