Persistent fatigue despite sufficient sleep. Weight gain without obvious dietary changes. Cold that is tolerated less well than before. Low mood for several months. Each of these symptoms, taken in isolation, can be explained by a thousand things. Together, they form a clinical picture that doctors recognize well: that of a slowing thyroid.
Hypothyroidism is one of the most common endocrine conditions in Quebec, and one of the most underdiagnosed, precisely because its manifestations blend into the background noise of daily life.
The role of the thyroid in the body
The thyroid is a small butterfly-shaped gland located at the base of the neck. It produces two main hormones, thyroxine (T4) and triiodothyronine (T3), which regulate the basal metabolism of almost every organ. Heart rate, body temperature, digestion, mood, weight, fertility, hair, and skin condition are all influenced, directly or indirectly, by thyroid activity levels.
When the thyroid gland produces too few hormones, your metabolism slows down. In fact, everything slows down. This is called hypothyroidism. It affects about 5% of the adult population in Canada, with a significantly higher prevalence among women and people over the age of 60 (Thyroid Foundation of Canada, 2022).
The most frequent symptoms
Fatigue is the most commonly reported symptom. Not a fatigue that goes away with a good night's sleep, but a deep-seated, persistent fatigue that sets in over weeks or months. It is often accompanied by a general feeling of slowness, both physically and cognitively. People sometimes describe difficulty concentrating, frequent forgetfulness, or the impression of functioning in slow motion.
Weight gain, often modest but unexplained, is another common sign. It is explained by a slowing of basal metabolism. Constipation, dry skin, fragile hair that falls out more, brittle nails, and cold intolerance complete the classic clinical picture. In some people, the thyroid gland is slightly enlarged, forming what is called a goiter, although this sign is absent in many cases.
In women of childbearing age, hypothyroidism can disrupt menstrual cycles and reduce fertility. In pregnant women, untreated hypothyroidism poses risks to fetal development, making it a condition that must be screened for and treated during pregnancy.
How is the diagnosis made
Diagnosis is based on a simple blood test. Measuring TSH, the pituitary hormone that stimulates the thyroid, is the first-line test. Elevated TSH indicates that the pituitary gland is working harder to try to stimulate an underactive thyroid, which reflects hypothyroidism. If TSH is abnormal, the doctor typically confirms and quantifies the hormonal deficiency with a free T4 measurement.
In some cases, particularly when the suspected cause is autoimmune thyroiditis, measuring anti-TPO antibodies can complement the assessment. Hashimoto's thyroiditis, the most common autoimmune form of hypothyroidism, is characterized by the presence of these antibodies, which gradually attack thyroid tissue.
Treatment and follow-up
Hypothyroidism is effectively treated with oral hormone replacement, usually with levothyroxine, a synthetic form of T4. The dose is gradually adjusted based on TSH results and clinical response. Once the dose is stabilized, TSH testing every six to twelve months is generally sufficient to ensure hormonal balance is maintained.
The majority of treated individuals regain normal energy levels and quality of life within a few weeks to a few months. Some symptoms, such as weight gain associated with hypothyroidism, gradually resolve with well-adjusted treatment.
Frequently Asked Questions about Hypothyroidism
Is hypothyroidism a permanent condition?
In most cases, yes. Hashimoto's thyroiditis, the most common cause, is a chronic condition that requires long-term treatment. In some cases, such as postpartum hypothyroidism, the condition can be temporary and resolve spontaneously.
Can diet influence the thyroid?
Certain nutrients play a role in the production of thyroid hormones. Iodine is essential for the synthesis of T3 and T4. Selenium and zinc are involved in the conversion of T4 to T3. A varied and balanced diet generally covers these needs without requiring specific supplementation, except in particular cases evaluated by a doctor.
Does levothyroxine have side effects?
At the right dose, it generally does not cause side effects. Too high a dose can cause symptoms of hyperthyroidism: palpitations, nervousness, insomnia, weight loss. This is why regular TSH monitoring is important to maintain balance.
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