What is the thyroid and what is it responsible for?

The thyroid gland is located in the neck and is needed to regulate the metabolism of all cells in the body. Therefore, when something goes wrong with the thyroid, chances are, you will notice that something isn't right. Dr Mark Vanderpump, a top consultant endocrinologist, explains the most common thyroid disorders (hyperthyroidism, hypothyroidism and thyroid nodules).

What is the thyroid?

The thyroid is a butterfly-shaped gland, which is situated just below your Adam’s apple (the larynx). A normal thyroid gland is neither visible nor can be felt if you apply finger pressure to your neck. It is the thyroid gland's job to produce hormones which regulate the metabolism of virtually all the cells in your body. This includes your temperature, heart rate, blood pressure and metabolism. It does this by producing two thyroid hormones - T3 and T4.

When there is too much thyroid hormone in the bloodstream it causes a condition called hyperthyroidism. When there is too little it is called hypothyroidism.

Hyperthyroidism 

This occurs when when your thyroid is overactive, about 1 in 100 people in the UK have this condition and it is six times more common in women.

As individual hyperthyroidism symptoms could relate to many other conditions, it’s not unusual for diagnosis to take 3-6 months - during which time you may have felt quite unwell.

Around ninety per cent of hyperthyroidism is caused by an autoimmune condition known as Graves’ disease. In Graves’ disease, antibodies stimulate thyroid cells to increase thyroid hormone production. Often, the thyroid becomes enlarged and becomes visible externally at which point it is known as a goitre. You can read more about goitres in my other detailed article on the topic. 

One third of those with Graves’ disease also develop a variety of eye problems (orbitopathy), including a staring appearance, grittiness, soreness, protruding eyeballs and, rarely, double vision or sight problems.

Other causes include benign thyroid nodules (nodular goitre), which are more common as we get older, or a temporary thyroid inflammation (thyroiditis) due to a virus or autoimmunity.

According to its type, hyperthyroidism and its side effects are usually treated with a combination of antithyroid drugs, radioiodine therapy, beta-blockers and, in some cases, surgery.

Hypothyroidism

If you have this condition, it means that you have an underactive thyroid which will then slow down your body’s metabolism. About 2 in 100 people in the UK have hypothyroidism and it is ten times more common in women.

Approximately seventy-five per cent of hypothyroidism is caused by an autoimmune condition called Hashimoto’s (whereby a goitre can also develop). The remainder are due to successful treatment of thyroid cancer, or an overactive thyroid which has then resulted in a far less dangerous underactive thyroid.

Early diagnosis of this condition is possible through greater awareness and an increased availability of blood tests. The current standard treatment is via the synthetic form of T4 called Levothyroxine which normalises and maintains the thyroid hormone levels.

Thyroid nodules

Appearing on their own or in clusters, a thyroid nodule is a solid or fluid-filled lump which can be caused by several different things:

• Lack of iodine in your diet in early childhood
• Abnormal growth of thyroid cells within your thyroid gland (a hyperplastic or colloid nodule)
• Thyroid adenoma (a benign tumour)
• A multinodular goitre comprising several nodules
• Thyroid cancer (those at highest risk are extremes of age (below 20 or above 70 years) and men more than women)

More than ninety-five per cent of thyroid nodules are harmless or benign. Thyroid nodules are more common in women and are more likely to occur as we age. Although most nodules don’t cause symptoms, they can become so large that they can be felt, seen or cause breathlessness or difficulty in swallowing as they press on your windpipe or oesophagus. In rare cases, there may even be hoarseness or difficulty speaking because of compression of a large nodule on the larynx.

Some nodules are described as “hot”, producing extra thyroid hormone which can then cause symptoms of hyperthyroidism. You can read more about thyroid nodules in my other article on the condition.

A few nodules are malignant, but most are slow growing and small when found. Aggressive thyroid cancer is uncommon but these nodules will be large, firm, fixed and fast growing. An ultrasound scan will be used to establish the size and number of nodules and whether a fine needle aspiration cytology (FNAC) to remove cells for microscopic examination will be required. This will help to decide whether it is benign or malignant. Sometimes the tests are not reassuring enough to give a definitive answer so surgery or ultrasound surveillance is advised.

If the tests reveal that the nodule/nodules are not causing any problems and are benign, then no further action is required unless there is evidence of increased growth of the nodule. Benign nodules can get bigger, but treatment is rarely required unless they are causing significant compression symptoms in the neck. A cancerous nodule will be removed surgically and you may then be treated with radioactive iodine. Around 90% of those identified with thyroid cancer will have a positive outcome.

Occurrence of thyroid nodules does tend to run in families and in those who have had an early childhood in areas that have been iodine deficient in the past, including Europe.

Dr Mark Vanderpump works in several top London medical institutes, including the Hospital of St John and St Elizabeth and The Platinum Medical Centre. To make an appointment with Dr Vanderpump, visit his Top Doctors profile.