Transient Neonatal Hypothyroidism Manifested at Birth

A 2 day-old male infant was referred to the Department of Paediatrics for a large goiter. The boy was born as the third child of healthy unrelated parents at 40 weeks of gestation with birth weight 4,950 g and length 55 cm. Antiseptics containing iodine were not used in the mother, nor in the infant. Physical examination revealed myxedema of the face, protruding tongue, dry skin, hoarse cry, large goiter and hypotonia. An ultrasound examination revealed enlarged thyroid gland. Thyroid function tests at 2 days of age were as follows: total triidothyronine (T3) 3.0 nmol/1 (normal range: 1.04-2.5), total thyroxine (T4) 23.2 nmol/1 (normal: 65-160), free thyroxine (fT4) 2.6 pmol/1 (normal range: 10-25), thyroid-stimulating hormone (TSH) 165.1 mIU/1 (normal range: 0.15-3.2), and thyroglobulin 2,093 ng/ml. He was immediately started on 50 g/day of L-thyroxine. Roentgenography of the knee demonstrated dysgenesis of the distal femoral epiphysis, while the proximal tibial epiphysis were not visualized. Molecular genetic analysis of the TPO gene was done. In the examined regions of the TPO gene, all 17 exons except exon 14, no mutations were detected. His mother's serum T4 and TSH levels were normal, and thyroglobulin and thyroperoxidase antibody tests were negative. There was no family history of thyroid diseases. No maternal use of medication was reported. Weaning off the L-thyroxine was started on the 23 day of life due to elevated T4 level. At the age of 4 months he was completely weaned off L-thyroxine and has not required any since. The patient is now 3.8 years old, thyroid enlargement is still present, and physical and neurological development are normal. Iodine overload, iodine deficiency, and matemal thyroid antibodies are common causes of transient congenital hypothyroidism. The etiology of transient hypothyroidism in this newborn is unknown. More research is required in order to evaluate the frequency, causes and optimal therapy of transient neonatal hypothyroidism.