ESPE Abstracts

Background: Congenital hypothyroidism (CH) is a common condition that occurs in ~1:3000–4000 live births and is one of the most common preventable cause of mental retardation with an early diagnosis and prompt pharmacological treatment. Neonatal screening has abolished this disease but 10% of children originally diagnosed with CH will have a transient form of the disorder and this percentage is increased during the last years due to a lowering of cut-off.

Aim: The schedules for re-evaluation of patients are different and factors useful to distinguish between transient and permanent CH are not well established. We enrolled 64 patients with a positive neonatal screening and eutopic thyroid gland that were re-evaluated at the age of three years, resulting to be affected both by permanent and transient CH. We aimed to identify factors useful to distinguish early between the two groups (A, transitory and B, permanent).

Results: None of the patients in group A (46 patients) required an increase of L-T₄ dose during the first three years of life but L-T₄ dose was increased in 16/18 patients (88.8%) in group B (P<0.0001). Mean L-T₄/kg body weight was significantly different between groups A and B at 1, 2, and 3 years of age respectively (2.3±0.8 μg/kg per day vs 3.8±1.0 μg/kg per day; 1.9±0.5 μg/kg per day vs 3.6±1.1 μg/kg per day; and 1.4±0.5 μg/kg per day vs 3.1±1.0 μg/kg per day, P<0.0001). The results of ROC curve analysis suggested that: i) L-T₄ requirements >4.9 μg/kg per day at 12 months or >4.27 μg/kg per day at 24 months are highly suggestive of permanent CH; ii) L-T₄ requirements <1.7 μg/kg per day at 12 months or <1.45 μg/kg per day at 24 months are highly suggestive of transient CH.

Conclusion: The analysis of L-T₄ requirements during the 1st years of life might allow an early discrimination between transient and permanent CH in eutopic patients.