The Proposed study is a double blind, randomized, placebo controlled study The aim of the study is to evaluate the effect of combined Growth Hormone (GH) treatment \& nutritional formula supplementation versus GH \& placebo on growth parameters in 64 children with Isolated Growth Hormone Deficiency (IGHD) after the 2nd year of GH treatment. In this trial GH is a background treatment (non-investigational medicinal product. Participants may be treated with any of the commercial GH products approved in Israel for the indication of IGHD. Participants will be randomly assigned either to the intervention group or the placebo control group. Randomization for the two study groups will be made in a ratio of 1:1. Both participants and study team will be blinded to the type of treatment that each patient will receive during the study. The randomization will be done according to gender and tanner stage. Participants in the intervention groups will be treated with the study formulas and participants in the control group will be treated with a placebo low caloric formulas (Powder added to water) The study will continue for 6 months of intervention versus active placebo, with additional 6 months (an extension period), in which participants at both groups, the intervention and the placebo, will be offered to continue their participation in the study with the active study supplement.