RESUMO
Mutations in the GHR locus may play a role in the cause of idiopathic short stature (ISS) by impairing growth-hormone (GH) receptor (GHR) function. At one extreme, mutations that nullify the function of the GH receptor are linked to complete GH insensitivity syndrome, or Laron syndrome, and we hypothesized that less-disruptive mutations could contribute to partial GH insensitivity syndrome. Low levels of GH binding protein may indicate mutations in the extracellular domain of the receptor, and by focusing on 14 children with ISS who had low GH binding protein and insulin-like growth factor I levels, we found three heterozygotes and one compound heterozygote for mutations in the extracellular domain of the receptor. We have since extended our study to a broader spectrum of patients, adding 76 patients with ISS who were treated with GH in a phase II study of the safety and efficacy of recombinant human GH in ISS and also adding 10 patients who were ascertained as having ISS by pediatric endocrinologists in private practice. The GHR gene has thus been analyzed in 100 patients with ISS, eight of whom were found to carry mutations: four in our original study and four with normal or elevated levels of GH binding protein. The latter group consists of three carriers of heterozygous extracellular domain mutations and one carrier of a heterozygous intracellular domain mutation. Family data suggest that the carriers of these mutations have a range of phenotypes, supporting our hypothesis that the expression of these heterozygous mutations as partial GH insensitivity syndrome depends on the genetic makeup of the person.
Assuntos
Estatura/genética , Transtornos do Crescimento/genética , Hormônio do Crescimento Humano/genética , Mutação/genética , Receptores da Somatotropina/genética , Proteínas de Transporte/sangue , Proteínas de Transporte/genética , Criança , Pré-Escolar , Mapeamento Cromossômico , Feminino , Regulação da Expressão Gênica , Genes/genética , Transtornos do Crescimento/tratamento farmacológico , Hormônio do Crescimento/uso terapêutico , Heterozigoto , Hormônio do Crescimento Humano/sangue , Hormônio do Crescimento Humano/uso terapêutico , Humanos , Fator de Crescimento Insulin-Like I/análise , Fator de Crescimento Insulin-Like I/genética , Masculino , Fenótipo , Polimorfismo Genético/genética , Polimorfismo Conformacional de Fita Simples , Receptores da Somatotropina/fisiologia , Segurança , SíndromeRESUMO
Long-term, low-dosage androgen treatment of patients with Turner syndrome results in more rapid growth and significantly greater adult height than in control patients who receive only estrogen for pubertal development. Seventeen patients treated with oxandrolone for one year and ten treated for two years had significantly greater growth velocities during than before treatment. Mean adult height of 25 patients treated with oxandrolone, fluoxymesterone, or both was significantly taller than the height of adult patients with Turner syndrome treated with estrogen only. Excessive skeletal maturation was not generally observed.