Some patients with a thyroid disorder may feel a swelling the neck. (Sheryl Nader/The Canadian Press)

Thyroid disorders — and there are several — affect about one in three Canadians, according to the Thyroid Foundation of Canada, which also estimates that about 50 per cent of these cases are undiagnosed. The disorders are up to seven times more common in women.

Mortality rates for patients with thyroid cancer have remained stable over the past decade, despite a rise in diagnoses, according to the Canadian Cancer Society. The uptick in cases, which was estimated to reach 4,300 in 2008, is attributed to improvements in diagnostic technology and greater use of ultrasounds, biopsies and magnetic resonance imaging.

What does the thyroid gland do?

It produces hormones that regulate physiological functions in your body such as metabolism, growth and development.

These hormones are essential for life. The two most important ones are tetraiodothyronine (thyroxine or T4) and triiodothyronine (T3). Both contain iodine.

Iodine is essential to the proper functioning of the thyroid. In some parts of the world — including the Great Lakes area of Canada and the U.S., the Swiss Alps and Tasmania — there is an iodine deficiency so iodine is added to most salt and bread.

The thyroid is part of the endocrine system of ductless glands that secrete hormones that are carried by the bloodstream to affect cells within specific organs. Other endocrine glands include the pituitary, adrenal glands, testes, ovaries and pancreas.

The thyroid is located in the middle of the lower neck, below the larynx and just above your collarbones. It is shaped like a butterfly.

How do I know if I'm having a problem with my thyroid?

There are several things that can go wrong with your thyroid, but the two most common are:

• Hypothyroidism — when the thyroid does not produce enough thyroid hormone.
• Hyperthyroidism — when the thyroid produces too much thyroid hormone.

Symptoms particular to each vary. You may have hypothyroidism if you are feeling run down, slow, depressed, sluggish, cold or tired, and exhibit dry skin and hair, constipation, muscle cramps or weight gain. Women may experience increased menstrual flow. Some people may also feel a swelling the neck due to an enlargement of the thyroid. This is also called goiter.

Symptoms of hyperthyroidism may include weight loss, nervousness, irritability, increased perspiration, a racing heart, hand tremors, anxiety, difficulty sleeping, increased bowel movements, fine brittle hair and muscular weakness — especially in the upper arms and thighs.

No one symptom will indicate that you have a thyroid problem. A diagnosis is made after a physical examination, and laboratory tests that measure the amount of thyroid hormone and thyroid stimulating hormone (TSH) in your blood. Your doctor may also order a thyroid scan, a chest x-ray or a CAT scan or Magnetic Resonance Image scan.

What are some of the other conditions linked to thyroid disorder?

A thyroid nodule is a localized swelling on the thyroid gland. Several nodules on the gland is not uncommon — especially among older people. It often causes no symptoms.

Single nodules affect about five per cent of the population; a single nodule can be cause for concern because it can indicate cancer of the thyroid. Cancer is far less likely when there are more than one nodule.

However, cancer of the thyroid is fairly rare and is highly treatable. Most thyroid cancers do not cause any symptoms. They rarely cause pain, difficulty in swallowing or hoarseness.

Another condition linked to hyperthyroidism is Graves' disease, which can cause inflammation of the eyes, swelling of the tissues around the eyes, bulging of the eyes or double vision. Eye problems are much more common in people with Graves’ disease who smoke.

How are thyroid conditions treated?

Hypothyroidism is treated by medication. Most people need to take thyroid hormone replacement pills every day for life. People on the medication need to undergo blood tests every year to make sure the dosage is correct. Major stress or illness can sometimes lead to an increased dosage.

Treatment for hyperthyroidism can be far more complex and will vary from patient to patient. Options include:

• Antithyroid drugs. These block your over-active thyroid's ability to make thyroid hormones.
• Radioactive iodine. Radioiodine is absorbed by overactive thyroid cells and destroys them. This course of treatment takes several weeks or months to be effective. Until then, antithyroid drugs may be used to control symptoms.
• Surgery. Most of the thyroid gland is removed to control hyperthyroidism.
• Beta-blockers. These won't change the high levels of thyroid hormones in your blood, but they can reduce the symptoms of a racing heart, the shakes, and nervousness.

Are thyroid problems inherited?

It's not common, but it does happen. Most cases of congenital hypothyroidism occur in people with no history of the disorder in their family. Up to 20 per cent of cases are inherited.

Most North American hospitals screen newborns for congenital hypothyroidism. One baby in 4,000 – 5,000 is being identified in Canada by screening tests. If not caught early and treated, the disease can lead to intellectual impairment and growth defects.