ESPE Abstracts (2015) 84 P-2-568

Levothyroxine Replacement in Primary Congenital Hypothyroidism: The Higher the Initial Dose the Higher the Rate of Overtreatment

Hale Tuhan, Ayhan Abaci, Gizem Cicek, Ahmet Anik, Gonul Catli, Korcan Demir & Ece Bober

Faculty of Medicine, Department of Pediatric Endocrinology, Dokuz Eylül University, Izmir, Turkey

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.

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