ESPE Abstracts

Objective and hypotheses: We analysed the prevalence of transient hypothyroidism in a cohort of children affected by CH with eutopic thyroid after Levothyroxine discontinuation.

Method: 77 newborns (36 females, 41 males) affected by CH with eutopic thyroid from 1999 to 2011 were enrolled. The confirmation diagnosis of CH after screening was made within the first 15 days of life by assessing TSH value (mean 74.4±82.2 μU/ml n.v 0.5–4.2) and fT₄ value (mean 8.9±3.6 pg/ml, n.v. 9–17). Thyroid ultrasound was performed in all newborn who were also treated with Levothyroxine at a starting daily dose of 5–10 mcg/kg per day (median dose 8.5 mcg/kg per day). All children were re-evaluated at a mean age of 3.5±1.0 years after treatment discontinuation for 4 weeks. They were divided in two groups according to TSH value at neonatal screening: group (A) TSH 7–U/ml and group (B) TSH >10.1 μU/ml (TSH cut-off value 7 μU/ml).

Results: Forty-seven children (61.0%) had transient hypothyroidism and 30 (39.0%) had permanent hypothyroidism; the latter had a mean TSH value at neonatal screening of 23.08±25.8 μU/ml (37.3% were in group A and 66.7% in group B) compared to the mean TSH value at diagnosis of 76.7±95.1 μU/ml. Children with transient hypothyroidism had a TSH value at neonatal screening of 16.6±16.1 μU/ml (40.4% were in group A and 51.1% in group B) compared to the mean TSH value at diagnosis of 75.1±87.7 μU/ml. No significant relationships were found between the two groups for their outcomes indicated as transient vs permanent hypothyroidism, mean TSH values at neonatal screening (P=0.79), at diagnosis (P=0.70), and dosage of Levothyroxine at diagnosis (P=0.12). Moreover, no correlation was found between mean TSH values at neonatal screening and after therapy discontinuation (r_s=0.15). Conversely, a significant relationship between the number of Levothyroxine therapy variations and the final outcome was found in children with permanent hypothyroidism (2.1±2.0) vs children with transient hypothyroidism (0.9±1.1; P=0.0097).

Conclusion: 39.0% of children with CH and eutopic thyroid presented true hypothyroidism after treatment discontinuation. Number of Levothyroxine therapy variations was the only significant factor as determinant of permanent hypothyroidism.