Introduction: Thyroid disorders are prevalent and their manifestations are determined by the dietary iodine availability.
Sources of data: Data from screening large population samples from USA and Europe.
Areas of agreement: The most common cause of thyroid disorders worldwide is iodine deficiency, leading to goitre formation and hypothyroidism. In iodine-replete areas, most persons with thyroid disorders have autoimmune disease.
Areas of controversy: Definition of thyroid disorders, selection criteria used, influence of age and sex, environmental factors and the different techniques used for assessment of thyroid function.
Growing points: Increasing incidence of well-differentiated thyroid cancer. Environmental iodine influences the epidemiology of non-malignant thyroid disease.
Areas timely for developing research: Iodine supplementation of populations with mild-to-moderate iodine deficiency. An evidence-based strategy for the risk stratification, treatment and follow-up of benign nodular thyroid disease. Is there any benefit in screening adults for thyroid dysfunction?