Hypothyroidism Symptoms: Causes & Treatment in Canada

Hypothyroidism symptoms can be subtle at first, but left unrecognized, an underactive thyroid can affect nearly every system in your body. Hypothyroidism occurs when your thyroid gland does not produce enough thyroid hormones — the chemical messengers that control how your body uses energy. This condition is common in Canada, especially among older women, and the good news is that it is highly treatable once properly diagnosed.

Recognising the Most Common Hypothyroidism Symptoms

Understanding the causes and treatment options for hypothyroidism is essential for Canadians who want to protect their long-term health. From Hashimoto’s thyroiditis to iodine deficiency, several factors can trigger an underactive thyroid. In this guide, we break down the early warning signs, risk factors, diagnosis process, and evidence-based treatments available through the Canadian healthcare system.

What Is Hypothyroidism?

Common Hypothyroidism Symptoms: Description and Severity Guide

Symptom	Description	Severity	When to See a Doctor
Fatigue and Low Energy	Persistent exhaustion that does not improve with rest; feeling sluggish throughout the day even after adequate sleep	Mild to Severe	If fatigue significantly interferes with daily activities or lasts more than a few weeks
Unexplained Weight Gain	Gradual increase in body weight despite no changes in diet or physical activity levels, often due to slowed metabolism	Mild to Moderate	If you gain more than 4–5 kg without a clear cause over a short period
Cold Intolerance	Increased sensitivity to cold temperatures; feeling unusually cold in hands, feet, or throughout the body when others are comfortable	Mild to Moderate	If cold sensitivity is persistent and accompanied by other hypothyroidism symptoms
Depression and Cognitive Changes	Low mood, difficulty concentrating, memory problems, and brain fog; often mistaken for primary depression or age-related cognitive decline	Moderate to Severe	Promptly if depression is new, worsening, or accompanied by physical symptoms such as weight gain or fatigue
Dry Skin and Hair Loss	Skin becomes rough, dry, and pale; hair may thin, become brittle, or fall out, including from the outer edge of the eyebrows	Mild to Moderate	If hair loss is diffuse or skin changes do not respond to moisturizers and topical treatments
Slow Heart Rate (Bradycardia)	Heart rate drops below 60 beats per minute; may cause dizziness, shortness of breath, or exercise intolerance in some individuals	Moderate to Severe	Seek prompt medical attention, especially if accompanied by chest discomfort, fainting, or difficulty breathing

Your thyroid is a small, butterfly-shaped gland at the base of your neck, just below your Adam’s apple. It produces two key hormones — T3 (triiodothyronine) and T4 (thyroxine) — that regulate your metabolism. A small gland in your brain called the pituitary gland controls thyroid function by releasing TSH (thyroid-stimulating hormone).

When the thyroid does not produce enough T3 and T4, the result is hypothyroidism. Your metabolism slows down, and over time, this can affect your heart, muscles, nerves, and more. According to Health Canada, thyroid disorders are among the most common hormonal conditions in the country.

Who Is Most at Risk?

Women are more likely to develop hypothyroidism than men. The risk also increases with age, especially for women over 60. However, hypothyroidism can affect people of any age, including newborns and teenagers.

In rare cases, babies are born with a non-functioning thyroid. This is called congenital hypothyroidism, and it affects roughly 1 in 4,000 newborns. Early treatment — within the first month of life — is essential to prevent developmental problems.

Common Causes of Hypothyroidism

There are several reasons why your thyroid may stop working properly. The most common cause in Canada is an autoimmune condition called Hashimoto’s thyroiditis.

Hashimoto’s Thyroiditis

In Hashimoto’s disease, your immune system mistakenly attacks your thyroid tissue. Over time, this damage reduces the thyroid’s ability to produce hormones. Hashimoto’s is the leading cause of hypothyroidism in countries like Canada, where iodine deficiency is not a major concern.

Worldwide, however, iodine deficiency remains the number one cause of hypothyroidism. In Canada, iodine is added to table salt and many foods, which has largely eliminated this problem.

Other Common Causes

• Thyroid surgery: Removing all or part of the thyroid — for conditions like hyperthyroidism, goitre, or thyroid cancer — can lead to hypothyroidism.
• Radioactive iodine therapy: This treatment for hyperthyroidism often reduces thyroid function permanently.
• Radiation therapy: External radiation used to treat cancers such as Hodgkin’s lymphoma can damage the thyroid.
• Certain medications: Lithium, amiodarone, and alpha-interferon are known to interfere with thyroid hormone production.
• Viral or bacterial infections: These can temporarily reduce thyroid function. In most cases, the effect is short-term.
• Pituitary or hypothalamus problems: Rarely, a problem in the brain — not the thyroid itself — prevents proper hormone signalling. These are called secondary or tertiary hypothyroidism.
• Too much iodine: Excess iodine from food or supplements can temporarily slow the thyroid. This is usually reversible.

Hypothyroidism and Pregnancy

Women can develop hypothyroidism during or after pregnancy. In fact, existing hypothyroidism may worsen during pregnancy. Postpartum thyroiditis — a thyroid condition after childbirth — is also a known cause.

Because symptoms like fatigue and low mood overlap with normal pregnancy experiences, hypothyroidism is sometimes missed. However, it is important to detect and treat it, as untreated hypothyroidism during pregnancy can affect the baby’s development.

Recognising the Symptoms of Hypothyroidism

Symptoms of hypothyroidism tend to develop slowly — often over months or even years. Because they appear gradually, many people do not notice them right away. Furthermore, mild symptoms are sometimes mistaken for normal signs of ageing.

Most Common Symptoms

• Feeling tired, weak, or sluggish even after enough sleep
• Feeling cold when others around you feel comfortable
• Dry skin and brittle nails
• Coarse or thinning hair
• Constipation
• Memory problems or difficulty concentrating
• Low mood or depression
• Slow movements or speech
• Irregular menstrual periods
• A yellowish tint to the skin

Less Common Symptoms

• An enlarged thyroid gland, known as a goitre, visible as a swelling in the neck
• Modest weight gain — often 4 to 5 kilograms or less
• Puffiness in the face, especially around the eyes
• Swelling in the arms, hands, or legs
• A hoarse or raspy voice
• Muscle aches and cramps

The severity of symptoms depends on your age, how long you have had the condition, and how low your thyroid hormone levels are. Mild or subclinical hypothyroidism often causes no symptoms at all. In older adults, hypothyroidism can be mistaken for Alzheimer’s disease or dementia because memory problems are a shared feature.

Symptoms During and After Pregnancy

During and after pregnancy, hypothyroidism symptoms can include extreme fatigue, dizziness, depression, and difficulty concentrating. Some women also develop a goitre. Because these symptoms overlap with common postpartum experiences, hypothyroidism is sometimes confused with postpartum depression. A simple blood test can tell the difference, so speak with your doctor if you have concerns.

Possible Complications of Untreated Hypothyroidism

When hypothyroidism goes untreated for a long time, it can lead to serious health problems. Therefore, early diagnosis and treatment are important.

In adults, untreated hypothyroidism can raise your cholesterol and triglyceride levels. This increases the risk of coronary artery disease and stroke. It can also cause fluid to build up around the heart, a condition called pericarditis.

In very severe cases, hypothyroidism can lead to a life-threatening condition called myxoedema coma. This is a medical emergency. As a result, anyone with severe or sudden worsening symptoms should seek emergency care immediately.

In children and teenagers, untreated hypothyroidism can slow growth and development. However, with proper treatment, most young people catch up to their peers in height and weight.

For more detail on complications and long-term management, the Mayo Clinic’s hypothyroidism overview is an excellent resource.

How Is Hypothyroidism Diagnosed and Treated?

Hypothyroidism is diagnosed with a simple blood test that measures your TSH level. If TSH is high, it means your pituitary is working overtime to stimulate a sluggish thyroid. Your doctor may also check your T4 level directly.

Treatment Options

The standard treatment for hypothyroidism is a daily oral medication called levothyroxine. This is a synthetic version of T4. It is safe, effective, and affordable — and it is covered under most provincial drug benefit programmes in Canada.

Most people feel significantly better within a few weeks of starting treatment. However, finding the right dose may take some time and require follow-up blood tests. Your doctor will monitor your TSH levels regularly to make sure your dose is correct.

Subclinical hypothyroidism — where TSH is slightly elevated but T4 is normal — may not always require medication. Your family doctor will help you decide the best course of action based on your symptoms and overall health.

Learn more about thyroid hormone therapy from Healthline’s guide to hypothyroidism treatments.

When to See a Doctor

If you notice several of the symptoms listed above — especially ongoing fatigue, unexplained weight gain, or feeling constantly cold — it is worth getting checked. These symptoms can have many causes, and a simple blood test is the first step.

In Canada, you can speak with your family doctor or visit a walk-in clinic to request a TSH blood test. Most provincial health plans cover this test when ordered by a physician. You do not need a specialist referral to get started.

If you are pregnant or planning to become pregnant and have a history of thyroid problems, let your doctor know as early as possible. Thyroid levels are often monitored throughout pregnancy to protect both you and your baby.

Seek emergency care right away if someone shows signs of myxoedema coma — such as extreme confusion, very low body temperature, or loss of consciousness.

Key Takeaways

• Hypothyroidism means your thyroid gland is not making enough hormones to keep your body running properly.
• The most common cause in Canada is Hashimoto’s thyroiditis, an autoimmune condition.
• Symptoms develop slowly and include fatigue, weight gain, feeling cold, dry skin, constipation, and low mood.
• A simple TSH blood test — available through your family doctor or walk-in clinic — can confirm the diagnosis.
• Treatment with levothyroxine is safe, effective, and covered by most provincial health plans.
• Untreated hypothyroidism can lead to serious complications, including heart problems and, in rare cases, myxoedema coma.
• Always speak with a healthcare provider before starting, stopping, or changing any thyroid medication.

According to Health Canada’s guidelines on thyroid health, this information is supported by current medical research.

For more information, read our guide on thyroid disorders and their causes in Canada.

This article is for informational purposes only and does not replace professional medical advice. Please speak with your family doctor or a qualified healthcare provider if you have concerns about your thyroid health or any of the symptoms described above.