Relationship of etiology to treatment in congenital hypothyroidism

We examined the patterns of TSH, T-4, and treatment schedules from diagnosi s to 4 yr of age in 125 children (50 males anf 75 females) with congenital hypothyroidism (CH). Subjects were divided into 3 groups based on their thy roid scans: 1) athyreosis (n = 31), 2) dysgenesis (n = 54; 49 lingual and 5 hypoplastic), and 3) dyshormonogenesis (n = 40). Follow-up evaluation was carried out at 2-4 wk and a, 6, 9, 12, 24, 36, and 48 months of age. Median gestational age, age at onset of therapy, and starting L-T-4 dose were sim ilar in the three groups. In infants with athyreosis median screening TSH l evels mere higher (P < 0.02) and confirmatory T-4 levels were lower than in the other two groups (P < 0.01 vs. dysgenetic; P < 0.05 vs. dyshormonogene tic GH). During the first 6 months of therapy, mean TSH levels were highest in the athyrotic group, intermediate in the dysgenetic group, and lowest i n the dyshormonogenetic group. In children with athyreosis, TSH levels norm alized by 12 months of age. At 12 months dysgenetic patients had the highes t TSH levels (P < 0.05). During the entire study period, TSH levels were lo west in patients with dyshormonogenesis (except at 48 months) and normalize d earlier. Mean T-4 levels normalized by 2-4 weeks in all groups. At 3 and 6 months, the percentage of patients who required dose changes was highest in the athyrotic group, and at 12 months it was highest in the dysgenetic g roup. The athyrotic group received the highest dose of L-T-4, and dyshormon ogenetic group received the lowest dose. We conclude that treatment and fol low-up schedules for CH may differ in the three etiological categories base d on the different hormonal patterns and responses to therapy. Children wit h athyreosis need close monitoring particularly early in life, whereas thos e with dysgenesis and dyshormonogenesis require more attention later in lif e.