ESPE Abstracts

Background: Congenital hypothyroidism (CH) is an important and preventable cause of growth retardation and neurological deficit. Early treatment is crucial to minimize long term effects and today regimens tend to be more aggressive targeting hormonal control.

Objective: To correlate CH severity at diagnosis with levothyroxine (LT) dosage and time needed to control TSH levels.

Methods: Retrospective study including children with CH at least 1 year of follow up (2005-2012). Variables included: age and severity at diagnosis, age at onset of treatment, TSH levels and LT dosage along time. CH was defined as mild (TSH: 20–40 mUI/l) and severe (TSH>40 mUI/l) and hormonal control was considered at date of TSH levels’ normalization. Statistical analysis: SPSS 21.

Results: We included 39 children, 27 females (69.2%). Mean TSH at screening was 164±125 mUI/l: 33 (84.6%) had severe CH (SCH), 6 (15.4%) had mild CH (MCH) (P<0.001). Comparing CH groups, age at the first visit was 18 days in SCH and 31 in MCH, (P=0.01); mean total LT dosage during the first year of treatment was 6.1±3.6 mcg/kg per day in MCH and 9.81±2.46 mcg//kg per day in SCH, (P=0.003). There was no significant difference in initial LT dosage between groups (7.9±2.6 mcg//kg per day in MCH, 9.3±3.0 mcg//kg per day in SCH; P=NS). LT was started at a median age of 36 days in MCH and 17 days in SCH (P<0.001). Hormonal control occurred at the mean age of 2.7±1.8 months in MCH and 4.2±3.6 months in SCH (P=NS). At 1 year of age we found a significant difference in LT dosage between groups (3.5±1.3 mcg//kg per day in MCH, 4.6±1.1 mcg//kg per day in SCH; P=0.03).

Conclusion: Babies with severe CH at diagnosis started treatment earlier, needed higher LT dosage and hormonal control occurred later than those with mild disease. This supports that LT initial dose should be higher in severe CH.