Dr. G - Health Column

Thyroid Diseases - Thyroid Cancer

The three most common types of thyroid cancer are papillary, follicular and medullary. Papillary thyroid cancer is one of the most curable cancers. The development of thyroid cancer is applicable to all ages. However, it is more common after the age of 30. Severity increases as patients become older. It is commonly found in women at a ratio of 3:1.

Follicular cancer is more common in adults between the ages of 40 and 60 and accounts for about 10-15% of all thyroid cancers. Females are at a three-time higher risk of developing it than males.

Medullary cancer is less common but more dangerous. The cancer spreads to multiple lymph nodes during the early stages and requires an extensive operation to remove the entire gland. This cancer is genetically inherited, so patients must be aware of their family history.

Are there any symptoms?

There are generally no symptoms associated with thyroid cancer apart from a lump developing in the neck. A feeling of pain is uncommon and is only present in an inflamed thyroid and present in rarer thyroid cancers such as medullary thyroid cancer.

Thyroid nodules

It is quite common for everyone to develop thyroid nodules as they are benign (non-cancerous). By the time we are 80, 90% of us will have at least one thyroid nodule. Fewer than 1% of these nodules are malignant (cancerous) and are identified by coincidence, through physical examinations of x-rays done for other purposes.

What should I do next?

• Fine needle biopsy can be done by inserting a needle into the thyroid nodule
• Another method is to remove the nodule and send it for a biopsy if thought to be cancerous
Patients who are younger than 50 with either papillary or follicular thyroid cancer have more than 98% chance of cure if treated properly. Patients are treated by completely removing the nodule that is cancerous. For the whole thyroid to be removed, the gland must have multiple nodules present that are cancerous.

How are thyroid cells unique?

They are unique as they absorb iodine which is required for thyroid cells to produce thyroid hormone. Most thyroid cells have the ability to concentrate iodine inside the cell, making it a target for cancer therapy. Radioactive iodine is given to patients with papillary or follicular thyroid cancer.

How does this work?

The radioactivity within the cancer cells destroys the cell itself from the inside. This method does not cause the regular symptoms such as hair loss or nausea. This method is non-toxic to most of our cells, however, it can affect the salivary gland, tear ducts or breast tissue if some iodine is absorbed, causing a potential risk to the patient.

Iodine deficiency disorder (IDD)

Iodine deficiency is the lack of iodine in our diet, which can cause goitre, the enlargement of the thyroid gland. Iodine is an important component needed to make the thyroid hormone. In children, iodine deficiency can cause mental disabilities. IDD is most common in developing countries as they lack access to healthy food but can also be found in developed countries in those whose diet contains sub-minimal iodine.

Who is at risk?

People likely to be deficient in iodine include vegans, vegetarians and pregnant women.

Iodine through our diet

Because our body does not naturally produce iodine, it needs to come from our diet. Foods rich in iodine include fish, eggs, dairy products and bread. Adults need around 150 mcg of iodine per day and pregnant/breast-feeding women need around 200 mcg a day.

Symptoms of IDD

i) Swelling of the thyroid gland to form a goitre
ii) IDD causes a variety of cognitive and physical problems in adults, children and infants. If it is left untreated, it can cause severe hypothyroidism, which can lead to:
•Heart disease
•Mental disabilities
•Nerve damage
•Impaired ovulation causing infertility in women
iii) Cretinism is another symptom characterized by stunted mental and physical growth
iv) Myxoedema is a life-threatening complication caused by IDD which can lead to unconsciousness

Testing for IDD

There are multiple ways to test for IDD, all of which vary in speed and accuracy.

Iodine loading test

is the most effective, where a patient needs to collect their urine samples over a 24-hour period to see how much iodine has been excreted. Although this method is not the most convenient, it is quite accurate.

Iodine patch test

A patch of iodine is painted onto the skin; if the patch takes longer than 24 hours to fade, the patient is confirmed to show no deficiency. If they are deficient, the iodine would have absorbed into the skin more quickly due to the current lack of iodine in the body.

Iodine supplements

If a person is not getting enough iodine in their diet, they are recommended to take iodine supplements. Supplements that contain potassium, such as potassium iodide, are effective as they are easily absorbed into the body. Excess supplements can be harmful to the thyroid.

What is Thyroid eye disease?

Thyroid Eye Disease (TED) affects the eye muscles and fatty tissue that surrounds the eye causing inflammation. It is an autoimmune disorder as the body’s own immune system attacks the muscles of the eye. It is mainly associated with patients who have hyperthyroidism but can occur in people with hypothyroidism or a normal functioning thyroid.

Symptoms of TED

• Inflammation
• Eyes can bulge and eyelids become red and swollen
• Extreme stiffness and swelling can cause the eyes to be misaligned, resulting in double vision
• In rare conditions, it can cause blindness if there is a lot of pressure on the optic nerve

TED can sometimes be misdiagnosed as other illnesses such as conjunctivitis or hay fever. Some ways to differentiate TED from other illnesses include having symptoms in the wrong season for hay fever, or not having sticky eyes that conjunctivitis would cause.

How does our thyroid affect our colour vision?

Thyroid development is also important for our visual cells in our retina. The retina is located at the back of our eye and turn images into electrical signals that are sent to the brain via the optic nerve. The cone visual cells in our eye are sensitive to light and determine what colour we see.

The human eye has two spectral cone types that contain visual pigments: UV/blue opsin responds to short wave light and green opsin responds to middle-to-long wave light. Thyroid hormone can reduce the usage of UV/blue light and begin to increase green opsin. This affects humans colour sensitivity and ability to see. Before it was thought that colour sensitivity of the cones in adults were fixed, but new research in mice suggests the amount of thyroid hormone we produce has an effect on our ability to see colour.

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