Many patients who require anaesthesia have coincidental disease of their thyroid gland. The thyroid gland is situated in the anterior region of the neck just deep to the strap muscles at the level of the C5 to T1 vertebrae. The structural units of the thyroid gland consist of round follicles, or acini, filled with colloid and surrounded by a single layer of epithelial thyroid cells. The signs and symptoms of hypothyroidism are predictable consequences of the physiological effects of the lack of thyroid hormones. Thyrotoxicosis affects approximately 2% of women and 0.2% of men in the general population. The prevalence of hyperthyroidism in iodine-sufficient areas is 2:1000 for overt and 6:1000 for sub-clinical hyperthyroidism. The indications for thyroidectomy include thyroid malignancy, obstructive symptoms, retrosternal goitre, Graves' disease unresponsive to medical treatment, recurrent hyperthyroidism, occasionally Hashimoto's disease and for cosmetic reasons.