Genetic analysis of the DUOX2 gene was performed in 11 children with organification defect. Two new mutations (Y1150C and A728T) and the deletion S965FsX994 were responsible for the deficit in the organification process and the phenotypes. Three polymorphisms (H678R, P982A, and R701Q) were identified.

Background: Levothyroxine (L-T 4 ) is commonly employed to correct hormone deficiency in children with congenital hypothyroidism (CH) and in adult patients with iatrogenic hypothyroidism. Objective: To compare the daily weight-based dosage of the replacement therapy with L-T 4 in athyreotic adult patients affected by CH and adult patients with thyroid nodular or cancer diseases treated by total thyroidectomy. Design and methods: A total of 36 adult patients (27 females and nine males) aged 18-29 years were studied; 13 patients (age: 21.5G2.1, group CH) had athyreotic CH treated with L-T 4 since the first days of life. The remaining 23 patients (age: 24G2.7, group AH) had hypothyroidism after total thyroidectomy (14 patients previously affected by nodular disease and nine by thyroid carcinoma with clinical and biochemical remission). Patient weight, serum free thyroid hormones, TSH, thyroglobulin (Tg), anti-Tg, and anti-thyroperoxidase antibodies were measured. Required L-T 4 dosage was evaluated. At the time of the observations, all patients presented free thyroid hormones within the normal range and TSH between 0.8 and 2 mIU/ml. Results: Patients had undetectable Tg and anti-thyroid antibodies. The daily weight-based dosage of the replacement therapy with L-T 4 to reach euthyroidism in patients of group CH was significantly higher than that in those of group AH (2.16G0.36 vs 1.73G0.24 mg/kg, P!0.005). Patients of group CH treated with L-T 4 had significantly higher serum TSH levels than patients of group AH (PZ0.05) as well as higher FT 4 concentrations. Conclusions: To correct hypothyroidism, patients of group CH required a daily L-T 4 dose/kg higher than group AH patients, despite higher levels of TSH. The different requirement of replacement therapy between adult patients with congenital and those with surgical athyroidism could be explained by a lack of thyroid hormones since fetal life in CH, which could determine a different set point of the hypothalamus-pituitary-thyroid axis.

Genetic analysis of TG gene was performed in two sisters affected by CH. A novel point mutation of the TG gene determining a stop codon at position 768 of the protein was identified. The early truncated nonfunctioning protein or the absence of the protein due to the premature degradation of abnormal mRNA may be responsible of the observed phenotype.