Endocrine Abstracts

Introduction: Congenital hypothyroidism is 30 times more frequent in newborns with Down syndrome (DS) than in the population of healthy children. Mild isolated TSH elevation with normal thyroxine (T4) levels is the most commonly seen pattern of thyroid dysfunction in these children.

Patients and methods: A retrospective study was carried out on eleven patients with DS in the pediatric department of Mahdia who were followed for congenital hypothyroidism.

Results: The average age of diagnosis of hypothyroidism was 3 months. Trisomy 21 was free in 10 patients and secondary to a translocation (46, XY, t rob (14;21),+21) in a single patient. Four patients had interventricular communication, 3 patients had atrial septal defects, 2 patients had arteriovenous communication and only one patient had cleft palate. Renal ultrasound was normal in all patients except one patient who had a moderate left pyelocalicial dilatation. Thyroid hormone tests were done after the discovery of an umbilical hernia in one patient and a neonatal jaundice in 3 patients; the thyroid assessment was then requested before the genetic confirmation of trisomy 21 by the karyotype. For the remaining 7 patients, hypothyroidism was discovered during a biological assessment requested as part of the systematic follow-up of these patients. The mean TSH value was 13.72 μU/ml. Hypothyroidism was subclinical in 4 patients (with normal T4 value). Cervical ultrasound showed a thyroid gland in place in all patients. No patients developed goiter. The initial mean dose of L-thyroxine was 7.25 μg/kg/d. After 3.25 years of follow-up, hypothyroidism proved to be transient in one patient while it was permanent in the others.

Conclusion: Newborns with DS have often subclinical hypothyroidism at birth. Systematic screening at birth and subsequent repeat screening is necessary because L-thyroxine administration will improve growth, hypotonia and psychomotor functions in these patients.