The thyroid is a gland in the neck that helps control many of the body’s most important functions.

If your thyroid becomes overactive (hyperthyroidism), underactive (hypothyroidism), or cancerous, you could experience a range of health problems.

Once diagnosed, however, thyroid problems can usually be treated effectively.

What is the thyroid?

The thyroid is a gland in the neck, near the base of the throat.

The thyroid gland makes hormones that help control many of the body’s metabolic processes, such as heart rate, blood pressure, body temperature and weight.

What types of thyroid problems are there?

The main types of thyroid problems are:

• Hyperthyroidism — this is when the thyroid is overactive and makes too much thyroid hormone. The most common symptoms of hyperthyroidism are feeling anxious or nervous, being unable to tolerate heat, having heart palpitations, feeling tired and losing weight, even if you’re eating the same amount of food. Hyperthyroidism is sometimes called thyrotoxicosis.
• Hypothyroidism — this is when the thyroid is underactive and does not make enough thyroid hormone. Hypothyroidism can go on for years without showing any signs. When symptoms do appear, they can be quite varied and can include fatigue, being unable to tolerate the cold, constipation, dry skin, weight gain, poor memory and depression.
• Thyroid cancer — this is when some of the thyroid cells become cancerous. Thyroid cancer is more common in women than in men and is usually diagnosed in people’s fifties. It can usually be treated successfully.

Other thyroid problems include nodules that grow in the thyroid, an inflamed thyroid, and an enlarged thyroid (goitre). These conditions may lead to either hyperthyroidism or hypothyroidism.

Because the thyroid gland plays an important role in controlling many of the body’s functions, serious health problems can result when it is not functioning as it should. If you think you may have a thyroid problem, it’s important to see your doctor.

What causes thyroid problems?

Problems with the thyroid can be caused by:

• iodine deficiency
• autoimmune diseases, in which the immune system attacks the thyroid, leading either to hyperthyroidism (caused by Graves’ disease) or hypothyroidism (caused by Hashimoto's disease)
• inflammation (which may or may not cause pain), caused by a virus or bacteria
• nodules, or non-cancerous lumps
• cancerous tumours
• certain medical treatments, including radiation therapy, thyroid surgery, and some medicines
• some genetic disorders

Occasionally, pregnancy can cause thyroid problems to start or get worse. If left untreated, this can cause problems for mother and baby, including miscarriage, premature birth, preeclampsia and bleeding after the birth.

What are the complications of thyroid problems?

If you have a thyroid problem that is not treated properly, serious health complications can result.

An overactive thyroid (hyperthyroidism) can lead to a number of problems including:

• eye problems, such as bulging eyes, blurred or double vision or even vision loss
• heart problems, such as rapid heart rate, problems with heart rhythm or heart failure — these problems can usually be treated
• brittle bones (osteoporosis)
• red, swollen skin — occurring particularly on the shins and feet
• thyrotoxic crisis, which is a worsening of symptoms causing fever, rapid heart rate and delirium — this requires urgent medical attention

An underactive thyroid (hypothyroidism) can cause a range of complications, including:

• an enlarged thyroid, or goitre, which may cause problems with swallowing and breathing
• high cholesterol and associated heart disease
• nerve damage causing tingling, numbness and pain in the legs, arms or other affected areas
• infertility
• birth defects
• miscarriage or premature birth
• mental health issues such as depression
• myxedema, which is a rare, life-threatening condition involving intense cold intolerance, lethargy and drowsiness that can lead to unconsciousness. Myxedema requires urgent medical attention