Phenotype: genotype relationships in growth hormone insensitivity syndrome

GH insensitivity syndrome (GHIS) is associated with many different mutations of the GH receptor (GHR) gene. We examined the phenotypic and biochemical features in 82 GHIS patients from 23 countries, each fulfilling diagnostic criteria of GHIS. There were 45 males and 37 females [mean age, 8.25 yr; mean height, -6.09 SD score, and mean insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3), -7.99 SD score]. Sixty-three were GH-binding protein (GHBP) negative; 19 were GHBP positive (> 10% binding). The mean height in GHBP-negative subjects was -6.5 SD score, and that in GHBP-positive patients was -4.9 SD score (P = < 0.001). Clinical and biochemical heterogeneity was demonstrated by the wide range of height (-2.2 to -10.4 SD score) and IGFBP-3 (-1.4 to -14.7 SD score) values, which were positively correlated (r2 = 0.45; P = < 0.001). This contrasted with the lack of correlation between mean parental height SD score and height SD score (r2 = 0.01). Fifteen different GH receptor gene mutations were identified in 27 patients. All had homozygous defects, except 1 who had a compound heterozygous defect. The mutations were 5 nonsense, 2 frame shift, 4 splice, 4 missense, and 1 compound heterozygote. There was no relationship between mutation type or exon of the GHR gene involved and height or IGFBP-3 SD score. In conclusion, GHIS is associated with wide variation in the severity of clinical and biochemical phenotypes. This variation cannot clearly be accounted for by defects in the GHR gene. Other genetic and/or environmental factors must, therefore, contribute to phenotype in GHIS.