The Thyroid and Thyroid Disease

The thyroid is butterfly-shaped gland located in the neck in front of your airway. It is made up of a right and left lobe, connected by a central area of thyroid tissue called the “isthmus”. The most important role of the thyroid gland is the secretion of the thyroid hormones; T3 and T4 (Thyroxine).

The role of the thyroid hormones relates to metabolic control. Specifically, higher levels of thyroid hormone;

• Increased metabolic rate and appetite
• Increase heart rate
• Increase body temperature
• Increase agitation
• Affect sleep patterns
• Increase gut motility

The levels of these hormones are usually kept under tight regulation by TSH, or Thyroid Stimulating Hormone, which is released by the pituitary gland. When investigating thyroid conditions, your GP will commonly order blood tests called thyroid function tests. These tests will include

• TSH
• T3
• Thyroxine (T4)

Disorders of thyroid function

Underactivity of the thyroid gland with low levels of T3 and T4 is known as Hypothyroidism, whereas overactivity of the thyroid gland results in high levels of T3 and T4 and is called Hyperthyroidism. These conditions can result from dietary issues (such as iodine deficiency or excess), abnormal TSH production, or from primary issues with the thyroid gland.

General symptoms associated with these conditions are listed in the table below.

Hyperthyroidism	Hypothyroidism
Cold intolerance and cold extremities	Increased heart rate and palpitations
Weight gain	Sweating
Tiredness and fatigue	Tremor
Constipation	Anxiety
Depression	Sleep disturbance
Reduced heart function	Diarrhoea
Hair loss	Weight loss

 

Other signs and symptoms may be present, relating to the underlying condition causing the abnormal levels of thyroid hormones.

Causes of thyroid dysfunction include;

Hyperthyroidism		Hypothyroidism
Condition	Description	Condition	Description
Toxic Nodule	An area of the thyroid gland that has become enlarged forming a “nodule” and secretes excessive amount of thyroid hormone.	Iodine Deficiency	As iodine is used by the thyroid gland to produce thyroid hormones, a deficiency of iodine can cause hypothyroidism
Toxic Multinodular Goitre	When a multinodular goitre forms one or more overactive nodules, resulting in increased thyroid hormone.	Hashimoto’s Thyroiditis	An autoimmune condition which results in the destruction of thyroid tissue, ultimately leading to decreased production of thyroid hormones.
Grave’s disease	An autoimmune disorder, causing a generalised enlargement of the thyroid gland. Variations in the disease in a minority of patients may cause hypothyroidism	Post Thyroid Removal	When the thyroid gland is removed your body can no longer make its own thyroid hormone, resulting in hypothyroidism.
Thyroiditis	Thyroiditis is inflammation of the thyroid gland and may be due to many different conditions, including Hashimoto’s Thyroiditis. Thyroiditis can be associated with increased thyroid hormone levels during inflammation but leads to hypothyroidism if there is progressive destruction of thyroid tissue.	Post Radiation Therapy	As above, radiation therapy to the thyroid results in loss of thyroid tissue.

 

Surgery for conditions with abnormal thyroid levels is usually only performed if an excess of thyroid hormone is unable to be controlled by medical measures. It may also be recommended if the condition is associated with another problem such as a goitre or thyroid nodule.

 

Thyroid Nodules

Thyroid nodules, or thyroid lumps, are actually very common and are mostly benign (non-cancerous). They may be picked up on ultrasound scan, examination by a doctor, or detected by a patient who has noticed a swelling or lump in their neck.

When seeing a patient with a thyroid nodule, they need to be further investigated to determine;

• What type of nodule is it? Is it cancerous?
• Is the nodule producing an excess of thyroid hormone (a “hot” nodule)?
• What is the size of the nodule and it is affecting other structures in the neck?

To help determine what type of nodule it is, you will need to have a sample of tissue taken from the nodule. This done with a Fine Needle Aspiration (FNA). An FNA is a simple procedure where a fine needle is inserted into the nodule under ultrasound guidance and samples of tissue from the nodule are taken. These tissue samples are looked at under the microscope and classified according to the Bethesda System;

Bethesda Score	Meaning
1	Non-diagnostic
2	Benign
3	Atypical lesion
4	Suspicious for Follicular Neoplasm
5	Suspicious for Malignancy
6	Malignant (cancerous)

 

Because only a small sample of the nodule can be obtained during FNA, the results cannot be 100% accurate, and even nodules classed as benign (Bethesda 2) do have a small chance of being cancerous. Final diagnosis can only be obtained once the whole nodule is removed via surgery and examined. Rather than used to diagnose, an FNA result is used by a surgeon to help determine the likelihood of a nodule being cancerous and guide the decision of whether a lesion should be observed or removed.

Dr Murugappan will discuss the results of your FNA and blood tests with you. With consideration of these results and the size and appearance of your nodule on ultrasound, she will discuss cancer risk, treatment options, and treatment recommendations with you.

 

Goitre

The term “goitre” is used to describe an enlargement of the thyroid gland. This may occur due to many reasons but is most commonly due to iodine deficiency or Graves disease. Not only can a goitre look unsightly, but it may also lead to compression of other structures in the neck. A patient with a large goitre may notice difficulty swallowing or redness in the face due to blood vessel compression. In severe cases, a goitre may even compress the airway and cause problems with breathing.

A goitre may warrant surgery if;

• It is large enough to cause a poor cosmetic appearance
• It is so large that it is at risk of compressing other structures in the neck
• It is producing excess hormone that cannot be controlled with medication
• It contains nodules that require surgical removal

Surgery of the Thyroid Gland