The study aims at identifying the predictive markers after one month of Saizen therapy in Growth Hormone Deficiency (GHD) and Turner Syndrome children. The study will recruit approximately 360 children in several countries worldwide. The study lasts for about the first one month of daily growth hormone treatment. There will be three clinic visits during the month of the study. There is an initial visit, then a visit before growth hormone treatment starts and finally a visit at the fourth week of treatment. The study requires two additional blood tests to a regular Saizen treatment follow-up. One sample is taken before growth hormone injections start and one additional blood sample is taken at the fourth week of treatment.