The thyroid gland has an important function in almost every aspect of human physiology. As well, its location in the neck allows for easy evaluation by the dentist. Part I of this paper reviews the normal functions of the thyroid gland as well as systemic effects caused by abnormal function. This is supplemented by easily-acquired methods of physical examination of the thyroid gland suitable for the dental practitioner. Part II is a case report highlighting the potential adverse effects of dental treatment of a patient who had poorly controlled thyroid function following total thyroidectomy.