The thyroid gland produces hormones critical to the maintenance of the cellular metabolic rate. The actions of these hormones are far-reaching, affecting thermoregulation and calorigenesis; the metabolism of carbohydrates, fats, and proteins; and oxygen utilization. Thyroid hormones also appear to act synergistically with epinephrine and enhance tissue sensitivity to catecholamines. Signs and symptoms of hypothyroidism include listlessness, fatigue, cold intolerance, dry skin, hair loss, constipation, weight gain, muscle soreness, and slow heart rate. Signs and symptoms of hyperthyroidism include irritability, heat intolerance, tremors, increased sweating, frequent bowel movements, and quickened heart rate. The effect of inadequately treated or undiagnosed hyperthyroidism on the heart carries perioperative risks. To provide competent dental care to patients with thyroid dysfunction, clinicians must understand the disease, its treatment, and the impact the disease and its treatment may have on the patient's ability to undergo and respond to dental care. Keywords: dental care, hyperthyroid, hypothyroid, thyroid dysfunction