Definitive diagnosis in children with congenital hypothyroidism.

Objectives: To investigate the definitive diagnosis and underlying causes of congenital hypothyroidism (CH) in eligible children through the use of a standardized protocol.

Study Design: Children > or =3 years of age with CH without an identified permanent cause underwent a diagnostic algorithm. Eligible subjects had an anatomically normal thyroid or had not undergone imaging studies. After thyroxine was discontinued for 4 weeks, thyroid function tests and a thyroid ultrasound were obtained. An abnormal ultrasound was followed by a (99m)Tc thyroid scan. A perchlorate washout test was performed in subjects with a normal ultrasound but abnormal thyroid function tests. Children with normal results were followed for 1 year.

Results: Of 33 children, 17 were boys. Nine (27%) had an absent or ectopic thyroid, 12 (36%) had dyshormonogenesis, and 12 (36%) had transient CH. Average thyroxine dose before medication discontinuation was 2.9 +/- 0.83 microg/kg in permanent cases versus 2.0 +/- 0.53 microg/kg in transient (P <.002). No complications from discontinuation of thyroxine occurred.

Conclusions: A significant percentage of children with CH have a transient requirement for thyroid hormone. A standardized protocol with thyroid ultrasonography is a safe and sensitive approach to a trial off of thyroxine in select patients.