Thyroid disorders are common in adolescence. Thyroid nodules can present in this age group, and although most are benign, malignancy is not unheard of. Chronic lymphocytic thyroiditis can present as hypothyroidism, while the adolescent with a goiter due to autoimmune thyroid disease is frequently euthyroid. Graves disease is a common etiology of hyperthyroid presentation in this age group. While there are known genetic and iatrogenic conditions that may predispose thyroid problems, they may also happen randomly in the general population. Thyroid problems may present as a goiter, a nodule, or a general cluster of abnormal symptoms and physical findings. The unique challenge to the provider of adolescent health care is that thyroid problems can adversely affect growth and development during puberty, a crucial period of hormonal interaction. This chapter addresses the diagnosis, treatment alternatives, and prognosis for a variety of common and uncommon thyroid abnormalities in adolescents. Many are readily treatable if recognized promptly, and even thyroid cancer often can be effectively treated and managed. Physicians treating the adolescent population have to be aware of the various thyroid problems that their patients can face.