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Isolated growth hormone deficiency type 1A in a Japanese family
Insights
A Japanese family with isolated growth hormone deficiency type 1A (IGHD 1A) was identified. The child had a homozygous deletion of the hGH-N gene, leading to growth arrest despite initial treatment.
Area of Science:
- Genetics
- Endocrinology
- Molecular Biology
Background:
- Isolated growth hormone deficiency type 1A (IGHD 1A) is a severe form of growth failure.
- Genetic defects in the human growth hormone gene (hGH-N) can cause IGHD 1A.
Observation:
- A 7-year-old Japanese child presented with IGHD 1A, confirmed to be homozygous for a deletion in the hGH-N gene.
- The child initially responded to human growth hormone (hGH) therapy but developed high hGH antibody titers, leading to growth cessation.
- Parents were heterozygous for the hGH-N gene deletion and exhibited impaired hGH response to stimuli but normal somatomedin-C levels and generation tests.
Findings:
- This case represents the fourth family reported with IGHD 1A due to hGH-N gene deletion.
- The inability to generate somatomedin-C, indicated by negative somatomedin-C generation tests, correlated with growth arrest.
- Restriction endonuclease analysis can differentiate this genetic cause from other autosomal recessive forms of severe hGH deficiency.
Implications:
- Genetic testing for hGH-N gene deletion is crucial for diagnosing IGHD 1A.
- Understanding the genetic basis of IGHD 1A aids in predicting treatment response and prognosis.
- This study highlights the importance of molecular diagnostics in pediatric endocrinology.
Abstract:
A Japanese family is described in which a 7-year-old child had isolated growth hormone deficiency type 1A, as described by Illig et al. He was shown to be homozygous for a deletion of the structural gene for hGH (hGH-N gene). Initially his growth rate responded well to hGH administration, but rapidly he developed high titers of hGH antibodies, and growth ceased. At that time, a somatomedin-C generation test gave negative results, suggesting that the growth arrest was related to the inability of hGH to generate somatomedin. Both parents were heterozygous for the hGH-N gene deletion and had a low hGH response to arginine and L-dopa tolerance tests, but had normal basal somatomedin-C levels and normal somatomedin-C generation tests. This family is the fourth to be reported with IGHD type 1A caused by deletion of the hGH-N gene. This cause of growth hormone deficiency can be distinguished from other severe autosomal recessive types of hGH deficiency by the demonstration of the deletion of hGH-N gene using restriction endonuclease analysis.