Thyroid Dr Gill Jenkins Dr Rob Hicks Thyroid illness is very common, especially as we age, and the gland can be over, or under, active.

In this article

What is thyroid illness? Symptoms

Causes and risk factors Treatment and recovery

The thyroid gland, which is in your neck, sets the rate at which you produce energy from your body's stores by the release of thyroid hormones. The thyroid gland controls metabolism through the production of thyroid hormone. It may become overactive (hyperthyroidism) or underactive (hypothyroidism).

If you're producing too much hormone, and the gland is overactive, you're said to be hyperthyroid, which affects 2 per cent of women and 0.2 per cent of men.

While if you’re not producing enough hormone, and the gland is underactive, you're said to be hypothyroid, which affects 2 per cent of women and 0.1 per cent of men.

In hyperthyroidism, symptoms may include:

• Weight loss
• Rapid heartbeat
• Tremor
• Excessive sweating
• Heat intolerance
• Anxiety
• Muscle weakness
• Goitre
• Irregular periods

If the gland is underactive as in hypothyroidism, the following symptoms may occur:

• Exhaustion, tiredness, sleep problems
• Difficulty concentrating or remembering
• Weight gain
• Dry hair, skin and nails
• Depression or anxiety
• Constipation
• Poor libido
• Breathlessness and swelling of feet
• Hoarseness
• Cold intolerance
• Face swelling and puffy eyes
• In women, heavy periods

Hyperthyroidism affects up to one in 50 people and can occur at any age, most commonly between 20 and 50.

There are many causes of an overactive thyroid and you may need blood tests and scans to find out what's responsible.

The most common reason is when your body's defences falsely recognise your own tissue as an invader and begin to attack it, although we don’t know what triggers this attack. This is called autoimmune disease and in this case, it stimulates the thyroid to produce more hormones.

If you have a nodule or growth in the thyroid, it may also produce too much hormone.

Rarely, taking certain medicines can make the thyroid produce more hormone. Hypothyroidism is ten times more common in women than in men and usually occurs over the age of 40. It can lead to high cholesterol levels and increase the risk of heart disease.

Again, there are many causes, but for some it seems to be part of the ageing process. Hypothyroidism is especially common in women after the menopause. Auto-Immune disease, both generalised and localised to the thyroid, can make the thyroid less active. Other causes of an under-active thyroid include treatments for over-active thyroid and genetic conditions such as Down's and Turner's syndrome.

It's difficult to prevent thyroid illness. Hypothyroidism is treated with thyroid hormone medication. Treatment of hyperthyroidism may involve medication to reduce the production of thyroid hormone, radioactive iodine therapy or a thyroidectomy (removal of part of the thyroid gland).

This article was last medically reviewed by Dr Gill Jenkins in June 2009.