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Linear growth in early treated children with congenital hypothyroidism
S Heyerdahl1, A Ilicki, J Karlberg
1Department of Paediatric Research, Rikshospitalet, Oslo, Norway.
Insights
Congenital hypothyroidism in children delays the onset of the childhood growth phase. Early thyroid hormone treatment is crucial for normal growth development, impacting the growth hormone-dependent phase.
Area of Science:
- Pediatrics
- Endocrinology
- Growth and Development
Background:
- Congenital hypothyroidism (CH) is a condition affecting thyroid hormone production from birth.
- Thyroid hormones play a critical role in early childhood development and growth.
- The infancy-childhood-puberty (ICP) growth model describes distinct phases of linear growth.
Purpose of the Study:
- To investigate the impact of CH on linear growth patterns in children.
- To analyze the timing of growth component onset in relation to CH and treatment.
- To determine the correlation between thyroid hormone levels, treatment initiation, and growth outcomes.
Main Methods:
- Studied growth from birth to 6 years in 103 children with CH using the ICP growth model.
- Compared growth patterns of CH children with reference data.
- Analyzed correlations between age at growth component onset, treatment start age, L-thyroxine dose, and height standard deviation scores.
Main Results:
- Children with CH exhibited reduced growth from 6-12 months and catch-up growth post-12 months.
- Onset of the childhood growth component was delayed in CH patients (girls: 10.4 months, boys: 11.0 months).
- Delayed onset correlated with later treatment start and, in severe CH, inversely with initial L-thyroxine dose. Height SDS change was linked to 1-year thyroxine levels.
Conclusions:
- Thyroid hormones in early life are essential for the normal onset of the childhood growth component.
- Delayed treatment initiation in CH negatively affects growth trajectory.
- Early diagnosis and treatment of CH are vital for optimizing growth and development.
Abstract:
Length/height was studied from birth to 6 years of age in 103 children with congenital hypothyroidism identified by the Norwegian or Swedish screening programs. We used the "infancy-childhood-puberty (ICP) growth model". This model describes normal linear growth during the first 3 years of life by an infancy component with the addition of a childhood component, the latter acting from the second half of the first year. In comparison with reference children, children with hypothyroidism had reduced growth from 6 to 12 months, and increased growth after 12 months of age. Mean onset of the childhood component of growth was delayed from 8.1 months (SD 1.9) to 10.4 months (SD 2.2) in girls, and from 8.9 months (SD 2.0) to 11.0 months (SD 2.1) in boys. Age at onset of the childhood component was correlated with age at start of treatment (r = 0.24), and in children with more severe hypothyroidism (pretreatment serum thyroxine < 40 nmol/l) inversely correlated with the L-thyroxine dose at start of treatment (r = -0.40). Change in height standard deviation score from 1 to 3 years of age was correlated with the serum thyroxine concentration at age 1 year (r = 0.30). The delay in the onset of the childhood component of growth and the association with age at start of treatment and initial L-thyroxine dose indicate that thyroid hormones during the first months of life are essential for normal onset of the childhood component of growth, which otherwise is assumed to be growth hormone-dependent.