Analysis of the intracellular signalling domain of the human growth hormone receptor in children with idiopathic short stature

Abstract

OBJECTIVE: To investigate the hypothesis that intracellular, dominant- negative mutations of the growth hormone receptor (GHR) exist in children with idiopathic short stature (ISS) and partial growth hormone insensitivity (GHI). SUBJECTS: We studied 31 children aged 4.55-13.14 years with ISS (height ≤ -1.8 standard deviation scores, UK standards 1990). GH provocation tests (glucagon 15 μg kg-1 i.m.) excluded GH deficiency in all subjects. Serum IGF-I levels were below the 50th centile for age in all subjects and below the 10th centile in 64.5% of cases. GH binding protein levels were normal in the 24 subjects in whom it was measured (mean 25.2%; range 10- 42.6%). METHODS: Exons 9 and 10 of the GHR were amplified by PCR from leucocyte-derived DNA. Samples were directly sequenced on the ABI 377 DNA analyser using the -21 M13 dye primer cycle sequencing protocol for optimum heterozygote detection. RESULTS: No abnormalities were detected in exon 9 which encodes the proline-rich box 1 motif. In exon 10 two sequence variants were found; a heterozygous, single base alteration (TCT to TCC) in codon 325 which does not change the amino acid sequence in one patient, and the L5261 variant in 24 subjects. L5261 is a conservative amino acid change and had an allele frequency of 0.53 in our patients, which is similar to that reported in a control population. CONCLUSIONS: The apparent partial growth hormone insensitivity in this group of idiopathic short-stature subjects is not related to heterozygous, dominant-negative variants of the intracellular signalling domain of the GHR. Hence it is likely that other genetic and environmental factors may be involved.