Background: It is possible that genes on the X chromosome are expressed differently depending of its parental origin. The objective of this study was to determine the influence of the parental origin of the X-chromosome on phenotypic variability, response to rhGH and on the biochemical profile of TS patients.Methods: This was a cross-sectional multicenter correlational study carried out over three years in six Latin-American university hospitals. Unrelated 45,X TS patients (n = 93; 18.3 ± 8.5 years )) were evaluated. A subgroup (n = 34) of the patients were prospectively treated with rhGH over two years. DNA profiles of patients and their mothers were compared to determine the parental origin of the retained X-chromosome through 10 polymorphic X-chromosome-STRs. The association with clinical features, biochemical profiles and anthropometric data at the beginning and after two years of rhGH treatment was determined.Results: Seventy two percent of patients retained the maternal X chromosome (Xm). A trend towards significance between maternal height and patients final height (p ≤ 0.07) in 45,Xm subjects was observed. There was no correlation between paternal height and patient height. No differences were detected between both groups in regard to dysmorphic features, classical malformations or increase in the height-SDS after rhGH. There were higher levels of triglycerides, total and LDL cholesterol in patients >20 years who retained the Xm.Conclusions: The parental origin of the retained X chromosome may influence lipid metabolism in TS patients, but its effect on growth seems to be minimal. No parental-origin-effect on the phenotypic features, associated anomalies and on the growth response to rhGH was found in 45,X TS individuals.

We have prospectively assessed the influence of GHR and VDR gene polymorphisms on the response to rhGH therapy in Venezuelan children with growth hormone deficiency (GHD, n=28) and Turner syndrome (TS, n=25). Clinical data during rhGH treatment were compared in GH and TS patients with different genotypes. PCR amplifications were performed to obtain the genotype frequencies of the polymorphisms. Clinical data at the start of treatment and rhGH doses were indistinguishable among patients with GHD or TS with different GHR or VDR genotypes. After the first two years of rhGH treatment, clinical data in both GHD and TS patients were not different according GHR or VDR genotypes. In addition, there was no significant difference among the subjects when both these genotypes were combined. Gene polymorphisms in low penetrance genes do not contribute to the rhGH therapy response in patients with GHD and TS.