Any enlargement or lump in the thyroid is called a goitre. Goitres are common, particularly in females of middle age, where about one in three will have a thyroid that can be felt clinically or is enlarged on ultrasound examination.
Most goitres are due to benign change, the most common in the form of multiple small lumps, the so-called multi-nodular goitre. These are not a risk factor for thyroid cancer and are left alone unless they are of a size that causes compression of other structures in the neck.
There is currently no guaranteed means of proving that a goitre is absolutely benign short of surgical removal, but thyroid cancer is rare. Investigations include Ultrasonography, (using sound waves to measure the thyroid) and fine needle aspiration for cytology (looking at cells removed through a needle from the thyroid). These tests are useful but only provide guidance, not proof of the nature of the lump or lumps.
The thyroid functions to produce a hormone (a chemical that circulates in the blood) called thyroxine, which determines amongst other things how fast the metabolism goes. If the thyroid is underactive (hypothroidism), too little thyroxine is released and symptoms including slowing down and weight gain could ensue. An overactive thyroid (hyperthyroidism) is more problematic and can cause a goitre, sweating and heart rate disturbances. Rarely surgery is indicated but it is usually treated with medications and radioactive iodine.