What is the thyroid gland?

The thyroid is a butterfly-shaped endocrine gland located in the lower half of the neck, in front of the trachea. It produces, stores and releases thyroid hormones, the key regulators of metabolism.

Thyroid hormones are essential for the proper function of all tissues and organs: they allow the body to use its energy reserves efficiently and keep the muscles working normally.

Who is at risk?

Thyroid dysfunction is very common worldwide, especially among women. In women, thyroid problems are more likely and may begin at a younger age. Certain periods of life — such as a recent childbirth or menopause — make a woman more susceptible to thyroid disease.

Hypothyroidism means an underactive gland, and hyperthyroidism an overactive one. Most patients with thyroid disease, however, have normal thyroid function (euthyroidism).

Regardless of your sex, the risk is higher if:

thyroid disease (hypothyroidism, hyperthyroidism, thyroid cancer) runs in your family;
you have an autoimmune disease such as type 1 diabetes;
you are over 60;
you have had thyroid disease or thyroid surgery in the past;
you have Down or Turner syndrome (risk of hypothyroidism);
you have ever taken lithium (risk of hypothyroidism);
you have taken excessive amounts of iodine-containing medicines;
you have received radiation (radiotherapy) to the neck area.
Fair-skinned people and Asians are at three times higher risk.

Hypothyroidism (underactive thyroid)

The symptoms of hypothyroidism can seriously affect both work and personal life. The most common symptoms are listed below.

If left untreated, hypothyroidism can lead to life-threatening complications: a marked slowing of metabolism and heart rate, heart failure, severe depression and coma.

fatigue, feeling unrefreshed after sleep;
cold intolerance;
weight gain or inability to lose weight despite dieting;
depression;
constipation;
menstrual irregularities or difficulty getting pregnant;
joint and muscle problems;
weak, brittle hair and dry skin;
reduced libido.

Hyperthyroidism (overactive thyroid)

In hyperthyroidism the thyroid releases too much hormone and the body's metabolism speeds up. It has various causes: Graves' disease, multiple nodules in the gland and some temporary forms of thyroid inflammation.

Graves' disease is passed down through families and is more common in middle-aged women.

Untreated hyperthyroidism can lead to heart rhythm disorders, high blood pressure, stroke or heart failure. In menopausal women it can cause osteoporosis and increase the risk of fractures.

Hyperthyroidism cannot be diagnosed from symptoms alone — a medical examination and blood tests are essential. Symptoms to watch for:

palpitations (heart rate over 90–100 beats per minute);
nervousness, irritability;
weight loss despite eating normally or more;
bulging eyes (typical of Graves' disease);
muscle weakness, especially in the upper arms and legs;
excessive sweating;
hand tremor;
thin, brittle hair;
soft, thin and moist skin.

Risk groups for hyperthyroidism

people with a family history of hyperthyroidism;
women, especially during pregnancy or in the first 6 months – 1 year after childbirth;
people with autoimmune diseases (type 1 diabetes, vitiligo, etc.);
smokers;
people taking excessive doses of thyroid hormone medication;
people with excessive iodine intake (e.g. iodine-containing medicines for heart rhythm disorders, intravenous iodinated contrast for imaging).

Goitre and nodules

Dietary iodine deficiency is the main cause of thyroid enlargement (goitre). About 700 million people worldwide are iodine deficient. The gland gradually enlarges and nodules form inside it. When the gland becomes very large, swallowing and breathing may become difficult.

A nodule is a round or oval lesion in the thyroid whose consistency differs from the surrounding tissue. There may be one or several. Nodules are very common: by the age of 60, half of all people have at least one. Like goitre, nodules may be related to dietary iodine deficiency.

A small nodule usually causes no discomfort and is found incidentally during a check-up, a neck ultrasound or a CT scan. When a nodule grows large, the following symptoms may appear — in that case, be sure to see a doctor:

difficulty swallowing or pain after swallowing;
difficulty breathing;
hoarseness;
symptoms of hyperthyroidism;
severe pain, fever, joint pain.

Thyroid cancer

Over the past 20–30 years the incidence of thyroid cancer has increased, while deaths from it have decreased.

There are 4 main types of thyroid cancer; they differ by the patient's age, tumour type, size and tendency to spread. Thyroid cancer is usually treatable, and surgery can cure it permanently.

Papillary cancer — 80–90% of all thyroid cancers. Occurs at any age, grows slowly and often spreads to the lymph nodes of the neck.
Follicular cancer — 5–10%. Grows slowly; can spread to the lymph nodes and, via the bloodstream, to distant organs such as bones and lungs.
Medullary cancer — a rare type, about 2% of cases. Shows up as a high blood calcitonin level and grows slowly. Some forms are hereditary, so these patients must undergo genetic mutation testing.
Anaplastic cancer — the rarest type, about 2% of cases. Grows rapidly, spreads widely and is difficult to treat.

Hashimoto's thyroiditis

Hashimoto's thyroiditis (chronic thyroiditis) is an autoimmune disease: the immune system mistakes healthy thyroid cells (thyrocytes) for “foreign” ones and destroys them. The gland is gradually damaged, produces less hormone as the disease progresses, and hypothyroidism may develop.

Sometimes a normal hormone level cannot meet the increased demand of pregnancy; in that case medication may be needed during pregnancy and breastfeeding. Afterwards the medication is stopped and thyroid function is checked to see whether it is sufficient.

The disease can occur at any age but is more common in middle-aged women and in people with a family history of thyroid disease. Why the immune system “attacks” the thyroid is not yet fully understood. Autoimmune diseases such as type 1 diabetes and vitiligo (white patches on the skin) increase the risk.

Symptoms:

fatigue, insomnia, weakness;
cold intolerance, feeling cold easily;
poor concentration, difficulty thinking;
depression;
weight gain;
swelling in the neck (goitre);
menstrual irregularities;
constipation;
joint and muscle pain;
hair loss, dry skin, brittle nails;
puffiness of the face and body.

Graves' disease

Like Hashimoto's thyroiditis, Graves' disease is related to the immune system, but here the thyroid is overstimulated and releases too much hormone (hyperthyroidism). Ophthalmopathy — inflammation and bulging of the eyes — is seen in 25–40% of patients with Graves' disease.

Women under 40 are particularly prone to this disease. The risk is higher in smokers and in people with a family history of Graves' disease.

The disease may go unnoticed for a long time, but watch for the following symptoms of hyperthyroidism:

palpitations;
nervousness, irritability;
persistent anxiety;
sleep disturbances;
weight loss despite normal eating;
excessive sweating, thinning of the skin;
menstrual irregularities;
hand tremor.

Symptoms of Graves' ophthalmopathy

redness, watering or inflammation of the eyes;
swelling of the tissues around the eyes;
bulging eyes;
rarely — double vision;
very rarely — loss of colour vision or complete loss of vision.

Diagnosis

The diseases described above are the most common thyroid diseases. If you notice any of these symptoms, see an endocrinologist without delay. The main diagnostic methods help identify the disease and choose the treatment:

medical examination;
laboratory tests (hormones and some biochemical markers);
ultrasound;
scintigraphy;
fine-needle aspiration biopsy (FNAB).

Thyroid diseases