Thyroid disease affects 1 in 20 people

Despite its small size the thyroid is an important organ, which plays a part in controlling metabolism of the body and its cells. It achieves this by producing two hormones called thyroxine (T4) and tri-iodothyronine (T3) and secreting them into the bloodstream. Iodine is an important constituent of these hormones. The activity of the thyroid gland is normally under the control of the pituitary gland, a small pea-sized structure that hangs from the base of the brain behind the eyes and on the skull. This is achieved by means of another hormone called Thyroid Stimulating Hormone (TSH). TSH helps to maintain normal levels of the thyroid hormones in the blood. T4 and T3 are carried in the blood stream by proteins. T4 is converted into T3 which is the active form. T3 crosses into cells to achieve its metabolic functions when it is not bound to blood proteins.

Thyroid disease is common and about one person in twenty will be affected at some point in their lives. All types of thyroid disease are more common in women and they often run in families, but this is unpredictable. Hypothyroidism (or an under active thyroid) is the most common of the disorders to affect the thyroid. Hyperthyroidism (or over active thyroid) and abnormal growth or enlargement of the thyroid gland (goitre or thyroid nodule) are also possible. Thyroglobulin is a tumour marker whose measurement may be appropriate after complete removal of the thyroid gland in those with thyroid cancer. It is not used for the diagnosis of thyroid cancer.