 Abstract congenital hyperthyroidism, CH, is a condition that affects one out of 2,000 to 4,000 newborns. It is characterized by subtle or absent symptoms at birth, which are likely caused by transpercental passage of maternal thyroid hormones. Infantile CH can also be caused by thyroid dyskinesis, which accounts for 85% of permanent primary CH cases. Dysalmonogenoses, which are inherited errors of thyroid hormone synthesis, account for 10% to 15% of cases. Secondary or central CH is usually associated with congenital hypothyroidism, which is caused by either isolated TSH deficiency or combined pituitary hormone deficiencies. Transient CH is most common in pre-term infants from areas of endemic iodine deficiency. Newborn screening programs have been implemented in many countries to detect CH, and infants are treated with levothyroxine. Treatment should begin immediately and consist of increasing the dose until the serum T4 level reaches 130 nmol per litre, 10 micrograms per December. This article was authored by LaFronche-Stevenh and Rastogi Manica V. We are article.tv, links in the description below.