Human growth hormone gene deletion without antibody formation or growth arrest during treatment--a new disease entity?

Using restriction endonuclease analysis of genomic DNA hybridized to a human chorionic somatomammotropin (hCS) complementary (c)DNA probe, we studied four young Jewish patients with isolated growth hormone deficiency (IGHD), and 15 family members. One family originated in Iraq, two in Yemen and one in Iran. Each patient was homozygous for a deletion of approximately 7.5 kilobases, which included the hGH-N gene. Three of the deletions were associated with the same restriction fragment length polymorphism haplotype, while the deletion in the child of Iranian descent was associated with a different haplotype. All the patients were treated with three injections per week of pituitary human growth hormone (hGH) for periods of 2 1/2 to 14 1/2 years. All had a good growth response. Three reached normal and one almost normal height. Repeated serum analyses revealed absence of anti-hGH antibodies. Thus, the presently described patients differ from those previously reported from Switzerland, Argentina and Japan, all of whom developed anti-hGH antibodies during treatment, with resultant slowing or arresting of growth. Expression of heterozygosity in family members was variable with regard to stature, hGH reserve and insulin-like growth factor I (IGF-I) levels. It is hypothesized that hGH-N gene deletion is not the sole determinant of immune response during hGH treatment, and that the difference between the current series and other cases needs further investigation.