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Evaluation of L-thyroxine replacement therapy in children with congenital hypothyroidism
L Chiovato1, L Giusti, M Tonacchera
1Instituto di Endocrinologia, University of Pisa, Italy.
Insights
L-thyroxine (L-T4) therapy effectively manages congenital hypothyroidism (CH) in children. Maintaining thyroid-stimulating hormone (TSH) below 5 microU/ml ensures normal free T3 and free T4 levels, promoting healthy growth without thyrotoxicosis.
Area of Science:
- Pediatric Endocrinology
- Neonatal Screening
- Thyroid Disorders
Background:
- Congenital hypothyroidism (CH) requires lifelong L-thyroxine (L-T4) replacement therapy.
- Optimal management strategies for CH in children are still being evaluated.
- Neonatal screening enables early diagnosis and intervention for CH.
Purpose of the Study:
- To evaluate the response pattern to L-T4 replacement therapy in children with CH.
- To determine the relationship between thyroid hormone levels and TSH in treated CH patients.
- To assess the safety and efficacy of L-T4 therapy regarding growth and development.
Main Methods:
- Study included 19 children with CH diagnosed via neonatal screening.
- Children were categorized into hypoplastic/aplastic thyroid disease (H/A) and gland ectopy (E) groups.
- Follow-up duration was 60 +/- 27 months, with L-T4 dosage adjusted to maintain TSH <= 5 microU/ml and normal FT3.
Main Results:
- Serum T4 levels at diagnosis differed between groups H/A and E.
- An inverse correlation was observed between serum TSH and FT4/FT3 concentrations.
- TSH levels <= 5 microU/ml were associated with FT4 in the upper normal range or higher, without adverse effects.
Conclusions:
- L-T4 therapy is effective in managing CH in children.
- Maintaining TSH within the target range ensures adequate FT4 and FT3 levels.
- Elevated FT4 alone with normal FT3 did not lead to thyrotoxicosis, growth issues, or craniosynostosis.
Abstract:
The outcome of L-thyroxine (L-T4) replacement therapy in children with congenital hypothyroidism (CH) remains to be completely evaluated. In this paper the overall pattern of response to L-T4 replacement therapy was studied in a group of 19 children with CH diagnosed by neonatal screening (10 with hypoplastic/aplastic thyroid disease, group H/A; 9 with gland ectopy, group E) who were followed-up for 60 +/- 27 months (mean +/- SD). With 1 exception serum T4 at diagnosis was greater than 2 micrograms/dl in children of group E and less than 2 micrograms/dl in those of group H/A. The initial dose of L-T4 (8-10 micrograms/kg BW/day) was modified in relation to age and weight in order to maintain serum TSH less than or equal to 5 microU/ml and FT3 in the normal range. A general inverse correlation between serum TSH and FT4 or FT3 concentrations was found, and the mean levels of serum FT4 and FT3 were significantly higher according to the following order of TSH results: low TSH (0-0.5 microU/ml) greater than normal (greater than 0.5-5 microU/ml) greater than elevated TSH (greater than 5 microU/ml). TSH levels less than or equal to 5 microU/ml were associated with FT4 values in the upper half of the normal range (54% of observations) or even higher (46%). Elevation of serum FT4 alone with FT3 values in the normal range did not result in clinical thyrotoxicosis, alteration of growth or premature craniosynostosis.(ABSTRACT TRUNCATED AT 250 WORDS)