Growth is a multifactorial process involving genetic, nutritional and other environmental determinants. Because of a major proportion of ultimate stature is dependent upon an intact growth hormone (GH) and insulin-like growth factor I (IGF-I) axis, much attention has been devoted to abnormalities related to these growth factors and their signalling pathways. At the tissue level, the action of GH result from the interaction of GH with a specific cell surface GH receptor (GHR). Thus, the ability of GH to exert biological effects is intimately linked to the number and function of GHRs in these tissue. In this study we analyzed the GHR gene expression in peripheral blood mononuclear cells of 31 idiopathic tall children (age: 11,59 ± 0,53 years; height: 2,69 ± 0,13 SDS), and 46 age and sex matched control children of normal stature (age: 10,57 ± 0,42 years; height: -0,24 ± 0,12 SDS) by Real-Time PCR. Normalization and validation of the data will be carried out using GADPH as housekeeping control gene and quantitative Real-time PCR data are expressed as agGHR/5X105 agGAPDH. We also measured circulating insulin-like growth factor I (IGF-I), by Immulite, in these children in order to investigate if a correlation between levels of this mediator and GHR gene expression level could exist. We found a significantly (p=0,029) higher GHR gene expression value in tall children (976.85 ± 653,4) compared to control children (86,81 ± 19,48); also IGF-I value was significantly (p=0,035) higher in tall children (0,87 ±0,11 SDS) than in control children (0,06 ± 0,19). In conclusion our preliminary data suggest that an up regulation of GHR gene expression could be responsible for the increased sensibility to GH in tall stature children.
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