What you need to know about thyroid health:
- The thyroid is a small gland in the neck that makes thyroid hormones. These hormones regulate key functions in the body.
- Most thyroid disorders are common and treatable, and diagnosis requires blood tests — symptoms and lab values alone don't tell the full story.
- About one in 10 Canadians are affected by a thyroid condition, with women affected more commonly than men.
Thyroid conditions are common and treatable.
According to the Thyroid Foundation of Canada, approximately one in 10 Canadians — that's four million people — are affected by some form condition that causes dysfunction in the body.
Despite how common thyroid conditions are, misconceptions about the gland persist.
What is the thyroid? What does it do?
The thyroid is a small, butterfly-shaped gland located in the lower part of the neck. It is wrapped around the airway (trachea).
It produces thyroid hormones — mainly T3 and T4 — that help regulate how the body works. These hormones affect nearly every organ and system, including metabolism, heart rate, body temperature, energy levels and digestion.
"These hormones are involved in the function of every cell in your body," says Dr. Phillip Segal, medical director of UHN's endocrinology clinics.
"I like to think about it as the gas or the speed regulator for your system."
What are common thyroid conditions?
Thyroid conditions typically fall into two main categories: hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid).
Each comes with its own set of symptoms.
Hyperthyroidism can cause:
- Weight loss without trying
- Increased hunger
- Increased (tachycardia) or irregular (arrythmia) heart rate
- Tremors, notably in hands
- Increased sweating
- Diarrhea
- Enlarged thyroid gland, sometimes known as a goiter
Hypothyroidism can cause:
- Weight gain
- Tiredness without cause
- Dry skin, brittle nails and hair loss
- Constipation
- Muscle pain and weakness
- Decreased heart rate (bradycardia)
- Feeling cold
The most common cause of underactive thyroid is Hashimoto's disease. The most common cause of overactive thyroid is Graves' disease.
"Both of these are autoimmune diseases, which means the body's immune system mistakenly attacks the thyroid," he says. "In fact, many common thyroid problems are caused by autoimmune conditions."
Thyroid disease can also be affected by family history (genetics), certain medications, radiation exposure, and, in rare cases, problems with iodine levels.
Myth: If I'm tired, gaining weight or anxious, it must be my thyroid
Truth: These symptoms can be caused by many factors — not just thyroid problems
Because thyroid hormones touch nearly every system in the body, the symptoms of dysfunction can look like a lot of other things, which is exactly why it can be difficult to pinpoint a diagnosis.
"It doesn't mean that if you have one of those symptoms, you automatically have thyroid problems," says Dr. Segal.
Weight, energy and mood are shaped by countless factors, from sleep and stress to diet and other medical conditions.
"There are so many things that go into someone's weight. Thyroid is only one of them."
Myth: I can tell if I have a thyroid problem based on symptoms
Truth: Symptoms are important but diagnosis requires laboratory testing
Symptoms and a physical exam may indicate potential concerns, but confirmation comes from the lab.
Doctors measure three key markers — thyroid stimulating hormone (TSH), T3 and T4 — to determine whether the thyroid is underactive, overactive or working as it should.
TSH is typically the first test ordered. If it comes back abnormal, T3 and T4 levels help pinpoint the issue.
Together, these results give a clearer picture than symptoms on their own.
Myth: I can interpret lab results on my own
Truth: Lab results need to be interpreted in clinical context
Seeing a laboratory test result flagged as high or low can be alarming, but those numbers don't tell the whole story.
Reference ranges are general guidelines. What's considered normal in the general population can differ depending on the individual, the reason the test was ordered and underlying conditions.
"What might be flagged as abnormal is in fact desired or normal for that situation," says Dr. Segal.
For example, in some patients treated for thyroid cancer, lab results may appear abnormal based on general population ranges, but are expected — or even desirable — based on their treatment and condition.
Myth: There is no cure for thyroid disease
Truth: Most thyroid conditions can be effectively managed with treatment
With the right diagnosis, thyroid disorders are among the most manageable chronic conditions.
Hypothyroidism is typically treated with daily hormone replacement.
Hyperthyroidism may be managed with medication, radioactive iodine or, in some cases, surgery.
"Getting the right diagnosis is key," says Dr. Segal. "From there, most thyroid conditions can be managed very effectively."
Myth: Men and women experience thyroid dysfunction equally
Truth: Thyroid dysfunction is diagnosed more often in women
The thyroid functions the same way in everyone, but women are significantly more likely to be diagnosed with thyroid conditions, particularly autoimmune diseases like Hashimoto's and Graves'.
"There are many possible reasons why thyroid disease is more common in women," says Dr. Segal.
"These include differences in the immune system, which make women more likely to develop autoimmune diseases. Hormones like estrogen can also affect how the thyroid works. Genetic factors may play a role as well."
Another possible reason is that women often see doctors more regularly and earlier, so thyroid problems are more likely to be found, he says.
That's part of why screening and awareness are important, especially for people with a family history of thyroid or autoimmune disease.
Myth: Thyroid dysfunction is a cause of thyroid cancer
Truth: They are separate conditions with different causes and presentations.
An overactive or underactive thyroid doesn't mean someone has — or will develop — thyroid cancer.
"If the thyroid is over‑ or underactive, that has nothing to do with thyroid cancer," says Dr. Segal.
Thyroid cancer tends to show different symptoms compared with thyroid conditions that cause dysfunction.
Rather than system-wide symptoms, such as fatigue or weight changes, thyroid cancer is usually detected physically as a lump in the gland that patients or doctors can see or feel.
When caught earlier, thyroid cancer typically has high survival rates.
Bottom line
Thyroid conditions are common, treatable and well understood — but they're also easy to miss or misread without medical input.
If something feels off, or if thyroid issues run in your family, talk to your health care provider about whether testing is appropriate.
