Hypothyroidism is one of the most frequent endocrine diseases; its signs and symptoms are explained by the inadequate production of thyroid hormones or their inadequate action in target tissues. According to the cause, hypothyroidism can be classified as congenital or acquired. It can arise as a primary dysfunction of the thyroid gland, in which there is a defect in thyroid hormone synthesis and hormonal release, or by a central defect from the hypothalamic-pituitary-thyroid axis. The etiology and clinical presentation of hypothyroidism in children and adolescents substantially differ from that in adults. Therefore, the identification of the specific clinical manifestations of thyroid dysfunction in childhood is fundamental to achieve an early diagnosis and treatment, which are essential to prevent multiple complications, especially devastating nervous system damage, and development delay. The aim of this review article is to describe the main characteristics of acquired hypothyroidism in pediatric age, through a simple clinical approach, useful to the daily general medical practice.