ESPE Abstracts

Background: Congenital hypothyroidism (CH) is the most frequent endocrine disorder during neonatal period and delay in diagnosis and treatment leads to irreversible complications. A high L-thyroxine (LT₄) dose is recommended for treatment, while the optimal starting dose is still a matter of debate.

Objective and hypotheses: The objective of this study was to determine the effects of various starting doses of LT₄ on serum thyroid stimulating hormone (TSH) and thyroxine (fT₄) at the end of the first month of treatment.

Method: A total of 71 patients (37 males) with CH were included in the study. The patients were divided into three groups according to the initial LT₄ doses: group 1 (n=24, 6–9.9 μg/kg per day), group 2 (n=21, 10–11.9 μg/kg per day), and group 3 (n=26, 12–15 μg/kg per day). A fT₄ level >2.3 ng/dl ±a TSH level <0.5 μIU/ml were considered as overtreatment.

Results: The mean age of the study population was 22.3±13.2 days at diagnosis. At diagnosis, the mean fT₄ was 0.84±0.32 ng/dl, and TSH was 39.3±30 μIU/ml. The mean initial dose of LT₄ was 10.9±2.9 μg/kg per day. Overtreatment rates were significantly different between the groups (group 1=25%, group 2=42.9%, group 3=61.5%, P=0.034) and significantly higher in group 3 compared to group 1 (P<0.0167).

Conclusion: None of the patients was undertreated. In this study, we found that the rate of overtreatment was significantly higher in patients who were given 12–15 μg/kg per day LT₄. Thus, monitoring thyroid functions earlier than one month of treatment is necessary.